U.S. patent application number 09/525841 was filed with the patent office on 2002-03-21 for flash photography system with preliminary and main emission.
Invention is credited to Sato, Yoichi, Takano, Takao, Tokunaga, Tatsuyuki.
Application Number | 20020034382 09/525841 |
Document ID | / |
Family ID | 27529081 |
Filed Date | 2002-03-21 |
United States Patent
Application |
20020034382 |
Kind Code |
A1 |
Tokunaga, Tatsuyuki ; et
al. |
March 21, 2002 |
FLASH PHOTOGRAPHY SYSTEM WITH PRELIMINARY AND MAIN EMISSION
Abstract
The present invention relates to a camera system which is
arranged to find the amount of emission of a main emission on the
basis of a measured light value obtained during a preliminary
emission, and perform control of the main emission. More
specifically, the present invention provides a camera system which
is arranged to inhibit processing, such as abnormal-reflection
correction, during execution of a specific kind of photography,
such as bounce flash photography, perform control processing suited
to the specific kind of photography, and execute correct
amount-of-light control.
Inventors: |
Tokunaga, Tatsuyuki;
(Saitama-ken, JP) ; Sato, Yoichi; (Kanagawa-ken,
JP) ; Takano, Takao; (Kanagawa-ken, JP) |
Correspondence
Address: |
ROBIN BLECKER & DALEY
2ND FLOOR
330 MADISON AVENUE
NEW YORK
NY
10017
US
|
Family ID: |
27529081 |
Appl. No.: |
09/525841 |
Filed: |
March 15, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09525841 |
Mar 15, 2000 |
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08685411 |
Jul 24, 1996 |
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6067422 |
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Current U.S.
Class: |
396/157 |
Current CPC
Class: |
G03B 7/09979 20150115;
G03B 7/08 20130101; G03B 7/17 20150115; G03B 7/09976 20150115 |
Class at
Publication: |
396/157 |
International
Class: |
G03B 015/03 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 28, 1995 |
JP |
HEI 07-193683 |
Jul 31, 1995 |
JP |
HEI 07-194908 |
Aug 16, 1995 |
JP |
HEI 07-208833 |
Aug 16, 1995 |
JP |
HEI 07-208835 |
Aug 21, 1995 |
JP |
HEI 07-212266 |
Claims
What is claimed is:
1. A camera system arranged to cause a preliminary emission to be
performed before a main emission is performed, and execute control
of the main emission according to a result of light measurement
performed during the preliminary emission, comprising: (a) a data
forming circuit for forming control data for controlling an amount
of emission of the main emission according to the result of the
light measurement performed during the preliminary emission; (b) a
control circuit for controlling the amount of emission of the main
emission on the basis of the control data supplied from said data
forming circuit; and (c) a correcting circuit for correcting the
control data according to camera condition data, a state of a flash
unit or the kind thereof or an operating state of the flash
unit.
2. A camera system according to claim 1, wherein said correcting
circuit is inoperative when the flash unit is in a bounce
state.
3. A camera system according to claim 1, wherein said correcting
circuit is inoperative when the flash unit is a ring flash
unit.
4. A camera system according to claim 1, wherein said correcting
circuit is inoperative when the flash unit is controlled at a
position away from a camera body.
5. A camera system according to claim 1, wherein said data forming
circuit forms the control data on the basis of first data according
to a difference between a measured light output obtained during the
preliminary emission and a measured light output obtained while the
preliminary emission is not being performed, and second data
according to a difference between a control exposure value and a
measured light output obtained while the preliminary emission is
not being performed.
6. A camera system according to claim 5, wherein said correcting
circuit corrects the first data.
7. A camera system according to claim 6, wherein said correcting
circuit sets the first data to a particular value when the first
data exceeds a predetermined value.
8. A camera system arranged to cause a preliminary emission to be
performed before a main emission is performed, and execute control
of the main emission according to a result of light measurement
performed during the preliminary emission, comprising: (a) a light
measuring circuit having a plurality of areas; (b) a data forming
circuit for forming control data for controlling an amount of
emission of the main emission according to a result of light
measurement performed by said light measuring circuit during the
preliminary emission; (c) a control circuit for controlling the
amount of emission of the main emission on the basis of the control
data supplied from said data forming circuit; and (d) a selecting
circuit for selecting a measured light value for use in said data
forming circuit from said plurality of areas according to camera
condition data, a state of a flash unit or the kind thereof or an
operating state of the flash unit.
9. A camera system according to claim 8, wherein said selecting
circuit selects a measured light value of a predetermined area from
among said plurality of areas in accordance with a first selecting
algorithm when the flash unit is in a predetermined state or of a
predetermined kind or in a predetermined operating state, or in
accordance with a second selecting algorithm different from said
first selecting algorithm when the flash unit is in a state
different from the predetermined state or of a kind different from
the predetermined kind or in an operating state different from the
predetermined operating state.
10. A camera system according to claim 9, wherein said selecting
circuit selects the predetermined area according to a focus
detecting point while using said first selecting algorithm.
11. A camera system according to claim 9, wherein the predetermined
state is a bounce state.
12. A camera system according to claim 9, wherein the flash unit of
the predetermine kind is a ring flash unit.
13. A camera system according to claim 9, wherein the predetermined
state is a state in which the flash unit is controlled at a
position away from a camera body.
14. A camera system according to claim 1, wherein said camera
system has a first operating state for performing the preliminary
emission in response to a shutter release operation and a second
operating state for performing the preliminary emission at an
arbitrary timing independent of the shutter release operation, said
correcting circuit being inoperative when said camera system is in
the first operating state.
15. A camera system according to claim 14, wherein said data
forming circuit forms the control data on the basis of first data
according to a difference between a measured light output obtained
during the preliminary emission and a measured light output
obtained while the preliminary emission is not being performed, and
second data according to a difference between a control exposure
value and the measured light output obtained while the preliminary
emission is not being performed.
16. A camera system according to claim 14, wherein said correcting
circuit corrects the first data.
17. A camera system according to claim 16, wherein said correcting
circuit sets the first data to a particular value when the first
data exceeds a predetermined value.
18. A camera system according to claim 9, wherein said camera
system has a first operating state for performing the preliminary
emission in response to a shutter release operation and a second
operating state for performing the preliminary emission at an
arbitrary timing independent of the shutter release operation, said
correcting circuit selecting said first selecting algorithm when
said camera system is in the second operating state.
19. A camera system comprising: (a) preliminary emission means for
performing a preliminary emission pointed at a subject; (b) a light
measuring circuit for measuring a light reflected from a subject
during the preliminary emission, and for measuring a luminance of
the subject while the preliminary emission is not being performed;
(c) a measuring circuit for measuring an amount of emission of the
preliminary emission through an optical path different from said
light measuring circuit during the preliminary emission; (d)
amount-of-main-emission computing means for computing a relative
amount of emission of a main emission with respect to the amount of
emission of the preliminary emission measured by said measuring
circuit, on the basis of a measured light value obtained from said
light measuring circuit; (e) backlight computing means for
computing a backlighting condition of a main subject on the basis
of a measured light value obtained from said light measuring
circuit while the preliminary emission is not being performed; and
(f) correcting means for applying a correction to a control value
of the amount of emission of the main emission computed by said
amount-of-main-emission computing means according to an output of
said backlight computing means.
20. A camera system according to claim 19, wherein the preliminary
emission performed by said preliminary emission means is a flat
emission which continues with a peak value kept constant for a
predetermined time.
21. A camera system according to claim 19, wherein said light
measuring circuit is a multiple divided light measuring circuit
which divides an image plane into a plurality of areas and performs
light measurement using the plurality of areas.
22. A camera system according to claim 19, wherein said correcting
means varies a correction value according to an output of said
light measuring circuit.
23. A camera system capable of controlling a flash unit, which is
arranged to perform a main emission pointed at a subject and
perform an exposure operation, comprising: (a) means for performing
a preliminary emission pointed at a subject; (b) light measuring
means for performing measurement of a light reflected from the
subject during the preliminary emission; (c) computing means for
computing an amount of emission of a main emission on the basis of
a result of the measurement of the reflected light; (d) flash-unit
control means for controlling the amount of emission of the main
emission on the basis of a computation result provided by said
computing means; and (e) a diaphragm setting circuit for setting a
diaphragm of a photographing lens to a fully open aperture value
before the preliminary emission.
24. A camera system capable of controlling a flash unit according
to claim 23, wherein the preliminary emission is a flat emission
which continues with a peak value kept constant for a predetermined
time.
25. A camera system capable of controlling a flash unit, which is
arranged to perform a main emission pointed at a subject and
perform an exposure operation, comprising: (a) means for performing
a preliminary emission pointed at a subject; (b) light measuring
means for performing measurement of a light reflected from the
subject during the preliminary emission; (c) computing means for
computing an amount of emission of a main emission on the basis of
a result of the measurement of the reflected light; (d) flash-unit
control means for controlling the amount of emission of the main
emission on the basis of a computation result provided by said
computing means; (e) a preliminary emission control circuit having
a first mode for causing the preliminary emission to be performed
immediately before the main emission and a second mode for causing
the preliminary emission to be performed independently of a
preliminary-emission operation; and (f) control means for causing
said camera system to perform continuous shooting in the second
mode while repeating the same amount of emission as an amount of
emission for a first frame.
26. A camera system capable of controlling a flash unit according
to claim 25, wherein the preliminary emission is a flat emission
which continues with a peak value kept constant for a predetermined
time.
27. A camera system capable of controlling a flash unit, which is
arranged to perform a main emission pointed at a subject and
perform an exposure operation, comprising: (a) means for performing
a preliminary emission pointed at a subject; (b) light measuring
means for performing measurement of a light reflected from the
subject during the preliminary emission; (c) computing means for
computing an amount of emission of a main emission on the basis of
a result of the measurement of the reflected light; (d) flash-unit
control means for controlling the amount of emission of the main
emission on the basis of a computation result provided by said
computing means; (e) a preliminary emission control circuit having
a first mode for causing the preliminary emission to be performed
immediately before the main emission and a second mode for causing
the preliminary emission to be performed independently of a
preliminary-emission operation; and (f) detecting means for
detecting whether a direction of an emission part of a flash unit
has been changed; and (g) mode changing means for changing the
second mode to the first mode if said detecting means detects that
the direction of the emission part has been changed.
28. A camera system capable of controlling a flash unit according
to claim 27, wherein the preliminary emission is a flat emission
which continues with a peak value kept constant for a predetermined
time.
29. A camera system comprising: mode setting means for setting a
photographing mode of a camera; flash means capable of performing a
flat emission; and flash-unit control means for inhibiting
photography using the flat emission if a predetermined
photographing mode is set by said mode setting means.
30. A camera system according to claim 29, wherein when the
predetermined photographing mode is not set, said flash-unit
control means inhibits the photography using the flat emission if a
measured light value is not greater than a predetermined value, or
enables the photography using the flat emission if the measured
light value exceeds the predetermined value.
31. A camera system according to claim 30, wherein said
predetermined value is calculated on the basis of an aperture value
of a photographing lens, a flash-synchronizing shutter speed of the
camera and a sensitivity of a film.
32. A camera system according to claim 29, wherein if said flash
control means inhibits the photography using the flat emission,
said flash control means enables photography using a flash
emission.
33. A camera system according to claim 29, wherein said
predetermined photographing mode is a full automatic mode.
34. A camera system according to claim 29, wherein said flash means
performs a preliminary emission and performs emission control of a
main emission on the basis of a measured light value obtained
during the preliminary emission, and said flash-unit control means
inhibits a flat emission during the main emission.
35. A camera system capable of controlling a flash unit, which is
arranged to perform a main emission, comprising: (a) a preliminary
emission circuit for causing said flash unit to perform a
preliminary emission; (b) a calculation circuit for calculating an
amount of emission of the preliminary emission according to a
photographing conditions; and (c) a determination circuit for
determining an amount of emission of the main emission on the basis
of a measured light output obtained during the preliminary
emission.
36. A camera system according to claim 35, wherein said
photographing condition is a voltage charged in a main capacitor
for storing flash emission energy.
37. A camera system according to claim 35, wherein said
photographing condition is a measured light output obtained while
the preliminary emission is not being photographed.
38. A camera system according to claim 35, wherein said
photographing condition is a distance to a subject.
39. A camera system according to claim 23, wherein said diaphragm
setting circuit sets the diaphragm to the fully open aperture value
if the preliminary emission is performed while the diaphragm is
being stopped down before the exposure operation.
40. A camera system according to claim 1, wherein said correcting
circuit corrects the control data on the basis of said camera
condition data.
41. A camera system according to claim 40, wherein said camera
condition data is a focal length of a lens.
42. A camera system according to claim 40, wherein said camera
condition data is a distance to a subject.
43. A camera system according to claim 8, wherein said camera
condition data is a focal length of a lens.
44. A camera system according to claim 8, wherein said camera
condition data is a distance to a subject.
Description
BACKGROUND 0F THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a camera system which
causes a flash unit to perform a preliminary emission before a main
emission, performs light measurement during the preliminary
emission and computes a correct control value of the main emission
on the basis of the result of the light measurement.
[0003] 2. Description of the Related Art
[0004] Various camera systems have heretofore been proposed as a
camera of the type which is capable of adjusting the amount of
emission pointed at a subject so that correct exposure is
automatically achieved. A system which is arranged to measure
the-subject-reflected light of the light emitted from a flash unit
and obtain the amount of correct emission has been widely used
because of its highly precise light measurement performance. One
example of such system is a TTL flash control system arranged to
find the amount of correct emission by measuring the
film-surface-reflected light of light which reaches a film surface
during exposure, and another example is a system arranged to
perform a preliminary emission pointed at a subject and control a
main emission so that the amount of emission of the main emission
is made equivalent to the relative amount of emission with respect
to the amount of emission of the preliminary emission.
[0005] In general, during flash photography, the light emitted from
a flash unit is directly projected onto a subject. However, bounce
flash photography is also often carried out by projecting the light
emitted from a flash unit to a ceiling or the like and illuminating
a subject with diffused light reflected from the ceiling or the
like.
[0006] FIGS. 46(a) and 46(b) schematically show different examples
of flash photography. FIG. 46(a) shows normal flash photography,
and FIG. 46(b) shows bounce flash photography. In the bounce flash
photography, a subject can be indirectly illuminated, so that it
can be photographed with soft light.
[0007] For the purpose of flash photography intended to emphasize
an three-dimensional effect, a flash unit may be made to emit light
toward a subject not from the same position as a camera body but
from a position away from the camera body. In this case, the flash
unit and the camera body cooperate with each other to perform
photography while exchanging information with each other in a wired
or wireless manner.
[0008] In addition, for the purpose of close-up photography
(macrophotography) of a subject, a ring type of flash unit having
an annular flash illumination surface capable of being disposed
around the periphery of a lens may be used so that a small subject
can be photographed on an enlarged scale in the state of being
illuminated with the light emitted from the flash unit.
[0009] However, in the conventional camera systems, in many cases,
the amount of emission in flash photography is controlled on the
assumption that the reflectance of a subject is similar to that of
a gray sheet having a 18% reflectance. This leads to the problem
that the amount of emission is controlled so that a white or black
subject is photographed as a gray subject. In addition, if a
regular reflection object, such as glass, is present on an image
plane, the luminance of the subject-reflected light of flash light
becomes extremely high, so that the amount of emission is
controlled to be reduced to an underexposure level which is greatly
low relative to a correct exposure level.
[0010] Japanese Laid-Open Patent Application No. Hei 4-331935 has
proposed a system which is arranged to cause a flash unit to
perform a preliminary emission before exposure, cause a multiple
divided light measuring sensor to measure subject-reflected light,
select a particular light measuring area on the basis of
information indicative of the amount of emission of the preliminary
emission and subject distance information, and perform a
computation for correcting the amount of emission of a main
emission, by using the measured light value obtained from the
selected light measuring area.
[0011] This system provides control based on normal flash
photography which is carried out on the assumption that the
distance from a camera to a subject is equal to the distance from a
flash unit to the subject. As a result, in the case of the
aforesaid bounce flash photography, the flash photography which is
performed in such a way that a subject is illuminated with flash
light from a position away from a camera, or the macrophotography,
the control of the selection of a light measuring area based on the
distance information and hence the computation of the amount of
emission of the main emission becomes meaningless, so that the
amount of emission may be incorrectly controlled.
[0012] In addition, this system has the disadvantage that even if a
photographer intends to control the amount of emission of the flash
unit so as to correctly expose a subject nearer to the camera than
an in-focus subject or intends to take an underexposure photograph,
as by intentionally placing a regular reflection object, such as
glass, or other high reflection objects in an image plane, the
system will perform a uniform correction of the amount of emission
or change light measuring areas to be used for control of the main
emission, thereby providing flash photography which does not
reflect the intention of the photographer.
[0013] In the conventional camera systems, if a subject is darker
than a background under backlight conditions, the intensity of a
stationary light component becomes higher than that of flash light.
As a result, if the area in the image plane of a backlit main
subject is smaller than the area of a light measuring sensor, a
correct measured light value cannot be obtained, so that when a
photographer slightly changes a composition, the state of exposure
greatly varies and so-called exposure unevenness occurs.
[0014] Japanese Laid-Open Patent Application No. Hei 6-250253 and
others have proposed that a decision is made as to whether a
subject is backlit and a control method is varied on the basis of
the decision. However, since there is only a combination of
backlight and non-backlight, exposure unevenness still occurs under
photographic conditions similar to backlighting conditions.
[0015] Many of the recent single-lens reflex cameras or the like
which use focal plane shutters have been designed so that a
photographer can select a flat emission mode for keeping the
emission intensity of flash light approximately constant (flat)
during the period from the instant when a shutter leading curtain
starts running until the instant when a shutter trailing curtain
completes running. The difference between the flat emission and the
flash emission whose emission intensity has a peak is shown in FIG.
47. Although the flash emission only allows flash photography to be
performed in the case of a shutter time which causes a shutter to
be fully opened, the flat emission allows flash photography to be
performed even in the case of a high-speed shutter time which uses
slit exposure.
[0016] Since the flat emission takes a longer emission time than
the flash emission as shown in FIG. 47, the guide number of the
flat emission is smaller than that of the flash emission. For this
reason, if the distance to a main subject is far or a large
aperture value is used in photography, the flat emission may
provide an underexposure compared to the flash emission.
[0017] Photographers who can understand the meaning of the guide
number will be able to predict occurrence of an underexposure.
However, beginners or the like who frequently make use of an
automatic exposure mode during photography and do not fully
understand the meaning of the guide number will have difficulty in
making such a prediction. Some of the beginners may have to check
warning displays of their cameras after the completion of
photography using the flat emission and newly perform photography
using the flash emission, or may forget to check such warning
displays and note an underexposure after the development of
photographs.
[0018] In the conventional TTL flash control system, the luminance
of a subject is measured indirectly and vaguely only at a
particular location in the image plane by making use of the
diffused light reflected by a film surface. This leads to the
problem that if the size or the composition of the subject varies,
exposure becomes instable and continuous photography (continuous
shooting) becomes difficult to perform with the same exposure
level.
[0019] The above-cited Japanese Laid-Open Patent Application No.
Hei 4-331935 has proposed the technique of causing a flash unit to
perform a preliminary emission before exposure, performing light
measurement of the preliminary emission, and correcting TTL flash
control at the time of a main emission. However, if the preliminary
emission is performed with the diaphragm of a photographing lens
stopped down for the purpose of viewing a depth of field or the
like, it is impossible to perform accurate light measurement, so
that accurate correction becomes impossible or a complicated
computation becomes necessary.
[0020] In addition, after the preliminary emission, if the
photographer is worried about an overexposure or the like and
deviates the direction of the emission part of the flash unit from
the subject, it is impossible to achieve correct correction by
using the measured light value obtained during the preliminary
emission without modification.
SUMMARY OF THE INVENTION
[0021] An object of the present invention is to provide a camera
system or a flash unit which is capable of perform correct control
of the amount of emission of a main emission according to the state
or the kind of the flash unit or the operating state thereof.
[0022] To achieve the above object, in accordance with one aspect
of the present invention, the flash unit is made to perform a
preliminary emission before the main emission and the amount of
emission of the main emission is computed according to the result
of light measurement obtained during the preliminary emission, and
whether the processing of correcting the computation is possible is
determined according to the state or the kind of the flash unit or
the operating state thereof.
[0023] In accordance with another aspect of the present invention,
there is provided a camera system or a flash unit which is arranged
to perform multiple divided light measurement during the
preliminary emission, select a predetermined light measuring area
from among the multiple divided light measuring areas according to
the state or the kind of the flash unit or the operating state
thereof, and perform correct control of the amount of emission of
the main emission on the basis of the measured light value of the
selected predetermined light measuring area.
[0024] In accordance with another aspect of the present invention,
there is provided a flash control system which is arranged to
perform a preliminary emission before a main emission during
photography and which comprises light measuring means for measuring
subject-reflected light during the preliminary emission, computing
means for computing a correction value of the amount of emission of
the main emission on the basis of measured light data according to
a measured light value detected by the light measuring means,
amount-of-light control means for controlling the amount of
emission of the main emission according to a computation result of
the computing means to make the amount of emission of the main
emission equivalent to a predetermined amount, and control means
for making the computation result of the computing means different
according to the operation of a photographer. Accordingly, the
flash control system is capable of inhibiting automatic correction
in accordance with the operation of the photographer and faithfully
reflecting the intention of the photographer.
[0025] In accordance with another aspect of the present invention,
there is provided a flash control system which is arranged to
perform a preliminary emission before a main emission during
photography and which comprises multiple divided light measuring
means for dividing an image plane into a plurality of areas and
measuring subject-reflected lights of the plurality of areas during
the preliminary emission, selecting means for selecting at least
one area from among the plurality of areas, changing means for
changing the selected area with another area on the basis of
measured light data according to a measured light value detected by
the multiple divided light measuring means, amount-of-emission
control means for controlling the amount of emission of the main
emission to make the amount of emission of the main emission
equivalent to a predetermined amount, with respect to the aforesaid
other area determined by the selecting means and the changing
means, and operating means for making the result of area changing
by the changing means different according to the operation of a
photographer. Accordingly, the flash control system is capable of
inhibiting the automatic change of the areas in accordance with the
operation of the photographer and faithfully reflecting the
intention of the photographer.
[0026] To solve the problem of backlight in the aforesaid
preliminary-emission type of camera system, in accordance with
another aspect of the present invention, there is provided a camera
system which comprises preliminary emission means for performing a
preliminary emission pointed at a subject, light measuring means
for measuring a light reflected from a subject during the
preliminary emission, and for measuring subject light while the
preliminary emission is not being performed, measuring means for
measuring the amount of emission of the preliminary emission during
the preliminary emission, amount-of-main-emission computing means
for computing the relative amount of emission of a main emission
with respect to the amount of emission of the preliminary emission
measured by the measuring means, backlight computing means for
computing the backlighting condition of a main subject on the basis
of a measured light value obtained from the light measuring means
while the preliminary emission is not being performed, and
correcting means for applying a correction to a control value of
the amount of emission of the main emission computed by the
amount-of-main-emission computing means according to the output of
the backlight computing means.
[0027] Another object of the present invention is to provide a
camera system or a flash unit which is arranged to perform a main
emission in the form of a flat emission and which can perform, if a
photographing mode which is frequently used by beginners is
selected as the mode of a camera, not the flat emission but a
normal flash emission so that even a beginner can take a photograph
without causing an underexposure.
[0028] To achieve the above object, in accordance with another
aspect of the present invention, if a measured light value is not
greater than a predetermined value, the flat emission is inhibited
to prevent occurrence of an underexposure.
[0029] In accordance with another aspect of the present invention,
there is provided a camera system of the type which controls a main
emission according to a measured light value obtained during a
preliminary emission and sets a diaphragm to a fully open aperture
(or an aperture value smaller than a predetermined value) during
the preliminary emission so as to perform correct light
measurement.
[0030] In accordance with another aspect of the present invention,
there is provided a camera system or a flash unit which is arranged
to perform a preliminary emission before a main emission and
perform light measurement of the preliminary emission and which
includes control means for executing, in each photographic cycle of
continuous shooting, a main emission according to a measured light
value obtained from a preliminary emission before a first
photographic cycle, so that it is possible to realize continuous
shooting capable of providing frames each having the same exposure
level, by making the amount of emission of the main emission in
each of a second photographic cycle et seqq. equal to the amount of
emission of the main emission in the first photographic cycle.
[0031] In accordance with another aspect of the present invention,
there is provided a camera system or a flash unit which is arranged
to perform a preliminary emission before a main emission and
perform light measurement of the preliminary emission and which
includes detecting means for detecting whether a photographing
condition has been changed and re-emission means for newly
performing a preliminary emission if the detecting means performs a
detecting operation before a main emission after the previous
preliminary emission, so that if a photographic condition, such as
the direction of the flash unit or a photographing mode of the
camera system, is changed after a measured light value obtained
from a first preliminary emission has been fixed, another
preliminary emission is performed before a main emission to carry
out accurate light measurement and correct main-emission control
according to the changed photographic condition.
[0032] The above and other objects and aspects of the present
invention will become apparent from the following detailed
description of preferred embodiments of the present invention,
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a diagrammatic cross-sectional view of a camera
system according to one embodiment of the present invention;
[0034] FIG. 2 is a schematic view showing the viewfinder of the
camera system shown in FIG. 1;
[0035] FIG. 3 is a block diagram showing the electrical circuits of
a camera body and a lens barrel which constitute the camera system
shown in FIG. 1;
[0036] FIG. 4 is a block diagram showing the electrical circuit of
a flash unit which constitutes the camera system shown in FIG.
1;
[0037] FIG. 5 is a flowchart of computation processing to be
performed by the camera system shown in FIG. 1;
[0038] FIG. 6 is a flowchart of computation processing to be
performed by the camera system shown in FIG. 1;
[0039] FIG. 7 is a flowchart of computation processing to be
performed by the camera system shown in FIG. 1;
[0040] FIG. 8 is a flowchart of computation processing to be
performed by the camera system shown in FIG. 1;
[0041] FIG. 9 is a flowchart of computation processing to be
performed by the camera system shown in FIG. 1;
[0042] FIGS. 10(a) and 10(b) are schematic views showing different
images displayed in the viewfinder of the camera system shown in
FIG. 1;
[0043] FIG. 11 is a flowchart of computation processing to be
performed by the camera system shown in FIG. 1;
[0044] FIG. 12 is a diagrammatic cross-sectional view showing a
camera system according to another embodiment of the present
invention;
[0045] FIG. 13 is a block diagram showing the electrical circuits
of a camera body and a lens barrel which constitute the camera
system shown in FIG. 12;
[0046] FIG. 14 is a flowchart of computation processing to be
performed by the camera system shown in FIG. 12;
[0047] FIG. 15 is a flowchart of computation processing to be
performed by the camera system shown in FIG. 12;
[0048] FIG. 16 is a flowchart showing one part of the operation of
another embodiment of a flash photography camera system according
to the present invention;
[0049] FIG. 17 is a flowchart showing the other part of the
operation shown in FIG. 16;
[0050] FIG. 18 is a flowchart showing the preliminary emission
control routine incorporated in the flowchart of FIG. 16;
[0051] FIG. 19 is a flowchart showing the subject area selecting
routine incorporated in the flowchart of FIG. 17;
[0052] FIG. 20 is a flowchart showing the abnormal-reflection
correcting routine incorporated in the flowchart of FIG. 17;
[0053] FIG. 21 is a flowchart showing the peripheral-area-reflected
light correcting routine incorporated in the flowchart of FIG.
19;
[0054] FIG. 22 is a flowchart showing another example of the
abnormal-reflection correcting routine of FIG. 19;
[0055] FIG. 23 is a flowchart showing another embodiment of the
present invention;
[0056] FIG. 24 is a flowchart showing the abnormal-reflection
correcting routine incorporated in the flowchart of FIG. 23;
[0057] FIG. 25 is a diagrammatic cross-sectional view of a camera
system according to another embodiment of the present
invention;
[0058] FIG. 26 is a block diagram showing the electrical circuit of
the camera system shown in FIG. 25;
[0059] FIG. 27 is a flowchart showing the operation of the camera
system shown in FIG. 26;
[0060] FIG. 28 is a diagrammatic cross-sectional view of a camera
body, a flash unit and the like which constitute a camera system
according to another embodiment of the present invention;
[0061] FIG. 29 is a block diagram showing the electrical circuit of
the camera system shown in FIG. 28;
[0062] FIG. 30 is a flowchart showing the operation of the camera
system shown in FIG. 29;
[0063] FIG. 31 is a flowchart showing the computation processing of
the camera system shown in FIG. 29;
[0064] FIG. 32 is a view showing an expression for calculating the
degree of backlighting and a graph representing the expression;
[0065] FIG. 33 is a view showing an expression for calculating the
amount of correction of the amount of emission and a graph
representing the expression;
[0066] FIG. 34 is a timing chart showing the timing of each
emission and light measurement;
[0067] FIGS. 35(a), 35(b) and 35(c) are graphs of different
functions for computing the amount of emission of preliminary
emission;
[0068] FIG. 36 is a block diagram showing the electrical circuit of
a camera system according to another embodiment of the present
invention;
[0069] FIG. 37 is an explanatory view aiding in describing a mode
setting dial of the camera system of FIG. 36;
[0070] FIG. 38 is a control flowchart of the camera system shown in
FIG. 36;
[0071] FIG. 39 is a control flowchart of a camera system according
to another embodiment of the present invention;
[0072] FIG. 40 is a program diagram of a camera body which
constitutes the camera system according to the embodiment shown in
FIG. 39;
[0073] FIG. 41 is an explanatory view showing the contents of an FP
emission enable flag provided in an MPU inside the camera body
which constitutes the camera system according to the embodiment
shown in FIG. 39;
[0074] FIG. 42 is a block diagram of the electrical circuit of a
camera system according to another embodiment of the present
invention;
[0075] FIGS. 43(a) and 43(b) are control flowcharts of the camera
system shown in FIG. 42;
[0076] FIG. 44 is a control flowchart of the camera system shown in
FIG. 42;
[0077] FIG. 45 is a table showing a light measuring method for the
camera system shown in FIG. 42;
[0078] FIGS. 46(a) and 46(b) are explanatory views aiding in
describing normal flash photography and bounce flash photography;
and
[0079] FIG. 47 is an explanatory view aiding in describing the
normal flash photography and the bounce flash photography.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0080] Preferred embodiments of the present invention will be
described below with reference to the accompanying drawings.
[0081] FIG. 1 is a diagrammatic cross-sectional view mainly showing
the optical arrangement of a flash photography camera system
applied to a single-lens reflex camera according to the present
invention.
[0082] The single-lens reflex camera shown in FIG. 1 includes a
camera body 1 in which the elements required for photography are
accommodated, such as optical parts, mechanical parts, electrical
circuits and film. A main mirror 2 is arranged to be obliquely
inserted into a photographic optical path or retracted therefrom
according to whether the shown camera is placed in an
observation-enabled state or a photography-enabled state. The main
mirror 2 is a half-mirror which, when it is obliquely inserted in
the photographic optical path, transmits approximately half of a
light ray reflected from a subject and received by the main mirror
2 to a focus detecting optical system which will be described
later.
[0083] A focusing screen 3 is disposed in a predetermined image
forming plane of a photographing lens system (12 to 14), and a
pentagonal prism 4 is provided for changing a viewfinder optical
path. A viewfinder 5 is arranged so that a photographer can observe
a photographic image plane, by observing the focusing screen 3
through the viewfinder 5. An image forming lens 6 and a multiple
divided light measuring sensor 7 are provided for measuring a
subject luminance in the photographic image plane which is being
observed by the photographer. The image forming lens 6
conjugationally relates the focusing screen 3 and the multiple
divided light measuring sensor 7 to each other via the
reflected-light optical path formed in the pentagonal roof prism
4.
[0084] The function of the multiple divided light measuring sensor
7 will be described below in detail. FIG. 2 is a schematic view
showing divided light measuring areas which are provided on the
photographic image plane. In FIG. 2, reference numeral 40 denotes
the entire photographic image plane, and reference numeral 39
collectively denotes the divided light measuring areas on the
photographic image plane which are to be used by the multiple
divided light measuring sensor 7 during light measurement. The
photographic image plane is divided into six light measuring areas
E0, E1, E2, E3, E4 and E5. The multiple divided light measuring
sensor 7 which is conjugationally related to the photographic image
plane in this manner is capable of measuring luminance values of
the respective divided light measuring areas on the photographic
image plane and outputting the measured luminance values.
[0085] The camera body 1 shown in FIG. 1 also includes a shutter 8
and a sub-mirror 25 which bends downwardly the reflected light ray
of the subject passing through the main mirror 2 and conducts the
light ray to a focus detecting unit 26. A photosensitive material 9
is a silver-halide film or the like.
[0086] A secondary image forming mirror 27, a secondary image
forming lens 28, a focus detecting line sensor 29 and the like are
provided in the focus detecting unit 26. The secondary image
forming mirror 27 and the secondary image forming lens 28 forms a
focus detecting optical system, which forms a secondary image
forming plane of a photographing optical system on the focus
detecting line sensor 29. The focus detecting unit 26 serves as an
automatic focus detecting device by detecting the state of focus of
a subject in the photographic image plane by a known
phase-difference detecting method and controlling a focus adjusting
mechanism for the photographing lens system, through processing
performed by an electrical circuit which will be described later.
This automatic focus detecting device is arranged to detect the
states of focus at predetermined three points in the photographic
image plane. FIG. 2 shows the positions of the three points as
distance measuring points P0, P1 and P2.
[0087] In FIG. 1, reference numeral 10 denotes a mount contact
group which serves as a known interface between the camera body 1
and a lens barrel 11. The lens barrel 11 is secured to the camera
body 1. The photographic lens system includes the lens groups 12 to
14. The first lens group 12 is arranged to move backward and
forward along the optical axis of the photographing lens system and
adjust the position of focus of an image to be photographed. The
second lens group 13 is arranged to move backward and forward along
the optical axis and vary the magnification of an image to be
photographed, i.e., the focal length of the photographing lens
system. The lens group 14 is a third lens group which is fixed.
Reference numeral 15 denotes a photographing lens diaphragm.
[0088] The operation of a first lens group driving motor 16 is
controlled in accordance with an automatic focus adjusting
operation to cause the first lens group 12 to move backward and
forward so that the position of focus can be automatically
adjusted. The operation of a lens diaphragm driving motor 17 is
controlled so that the photographing lens diaphragm 15 can be
opened and closed.
[0089] An external flash unit 18 is secured to the camera body 1,
and executes emission control in accordance with a signal supplied
from the camera body 1. The flash unit 18 includes a xenon tube 19
which converts electric-current energy into emission energy, a
reflector 20 and a Fresnel lens 21. The reflector 20 and the
Fresnel lens 21 have the role of efficiently gathering light of the
emission energy toward a subject. Reference numeral 22 denotes a
known flash contact group which serves as an interface between the
camera body 1 and the external flash unit 18.
[0090] The flash unit 18 also includes a glass fiber 30 which
conducts light emitted by the xenon tube 19 to a monitoring sensor
(PD1) 31. The sensor (PD1) 31 directly measures the amounts of
emissions of a preliminary emission and a main emission of the
flash unit 18, and is provided for control of the amount of
emission of the main emission, which control constitutes a feature
of the present invention. A sensor (PD2) 32 is provided for
monitoring light emitted by the xenon tube 19. By restricting the
emission current of the xenon tube 19 according to the output of
the sensor (PD2) 32, the flash unit 18 can be made to perform a
flat emission.
[0091] The flash unit 18 has the bounce flash function of varying
the direction of an emission part independently of the optical axis
of the photographing lens system. A switch 33 is provided for
detecting whether the flash unit 18 is in a bounce state.
[0092] Although FIG. 1 shows only the optical parts selected from
among all the elements required for realizing the present
invention, it is a matter of course to need various other
electrical circuit parts none of which is shown.
[0093] FIGS. 3 and 4 show block diagrams of electrical circuits of
the present camera system. In FIGS. 3 and 4, identical reference
numerals are used to denote constituent elements identical to those
shown in FIG. 1. FIG. 3 shows a circuit block diagram of the camera
body 1 and the lens barrel 11, and FIG. 4 shows a circuit block
diagram of the flash unit 18.
[0094] A camera microcomputer 100 performs a required computation
processing operation on the basis of a clock signal produced by an
oscillator 101.
[0095] An EEPROM 100b stores a film count value and other
photography information. An A/D converter 100c performs A/D
conversion of analog signals supplied from a focus detecting
circuit 105 and a light measuring circuit 106. The camera
microcomputer 100 sets various states by performing signal
processing of a digital value supplied from the A/D converter
[0096] The focus detecting circuit 105 and the light measuring
circuit 106 as well as a shutter control circuit 107, a motor
control circuit 108, a film running detecting circuit 109, a switch
sense circuit 110 and an LCD driving circuit 111 are connected to
the camera microcomputer 100.
[0097] The transmission of signals between the camera microcomputer
100 and a lens microcomputer 112 disposed in the lens barrel 11 is
carried out via the mount contact group 10. If the flash unit 18 is
attached directly to the camera body 1, the transmission of signals
between the camera microcomputer 100 and a flash-unit microcomputer
200 disposed in the flash unit 18 is carried out via a flash
contact group 22. The camera body 1 also includes a
transmitting/receiving circuit 113, an infrared light receiving
sensor 50 and a transmitting infrared LED 51. The camera
microcomputer 100 can perform communications with the flash unit 18
(the flash-unit microcomputer 200) which is spatially remote from
the camera body 1, via these elements 113, 50 and 51.
[0098] The focus detecting line sensor 29 is a known CCD line
sensor composed of three line sensors Line-L, Line-C and Line-R
which correspond to the above-described three distance measuring
points P0, P1 and P2. The focus detecting circuit 105 performs
storage control and reading control of the focus detecting line
sensor 29 in accordance with a signal supplied from the camera
microcomputer 100, and outputs pixel information read from the
respective line sensors Line-L, Line-C and Line-R to the camera
microcomputer 100. The camera microcomputer 100 performs A/D
conversion of the pixel information and performs focus detection
based on a known phase-difference detecting method. The camera
microcomputer 100 performs an exchange of signals with the lens
microcomputer 112 on the basis of the focus detection information,
to adjust the focus of the photographing lens system.
[0099] The light measuring circuit 106 outputs to the camera
microcomputer 100 the output from the multiple divided light
measuring sensor 7 having the photographic image plane divided into
the six light measuring areas E0, E1, E2, E3, E4 and E5 as
described previously, i.e., the luminance signals of the respective
light measuring areas in photographic image plane. The light
measuring circuit 106 outputs luminance signals both when the flash
unit 18 is in a steady state in which the flash unit 18 has not yet
performed a preliminary emission of flash light toward a subject
and when the flash unit 18 is in a preliminary emission state in
which the flash unit 18 has performed the preliminary emission. The
camera microcomputer 100 performs A/D conversion of the luminance
signals, and performs a computation on an aperture value to adjust
the amount of exposure for photography, a computation on a shutter
speed, and a computation on the amount of emission for the main
emission of the flash unit 18 during an exposure.
[0100] The shutter control circuit 107 causes a shutter leading
curtain (MG-1) and a shutter trailing curtain (MG-2) to run to
control an exposure operation, in accordance with a signal from the
camera microcomputer 100.
[0101] The motor control circuit 108 controls a motor M in
accordance with a signal from the camera microcomputer 100, to
cause the motor M to move the main mirror 2 up and down, charge the
shutter 8 and transport the film 9.
[0102] The film running detecting circuit 109 detects whether the
film 9 has been wound by one frame during a film transport, and
sends a signal indicative of the detection result to the camera
microcomputer 100.
[0103] When a release button (not shown) is pressed to a first
stroke position, a switch SW1 is turned on to start a light
measuring operation and an automatic focusing (AF) operation. When
the release button is pressed to a second stroke position, a switch
SW2 is turned on to start an exposure operation. A switch SWFELK is
interlocked with a push switch (not shown). If the photographer
points the camera system at a subject to which to correctly adjust
the amount of emission of the flash unit 18 before starting an
exposure operation and depresses the push switch (the switch
SWFELK) with the subject located at a particular position on the
photographic image plane within the viewfinder 5, the flash
photography camera system performs a preliminary emission and
memorizes the amount of correct emission of the flash unit 18
relative to the subject, and controls the amount of emission of the
flash unit 18 during the main emission in accordance with the
memorized amount of correct emission.
[0104] The switch sense circuit 110 senses signals supplied from
the switches SW1, SW2 and SWFELK and other camera operating members
(not shown) and sends them to the camera microcomputer 100.
[0105] When the shutter 8 is fully opened, a switch SWX is turned
on to instruct the flash unit 18 of an emission timing at which to
perform the main emission during an exposure operation.
[0106] The liquid crystal display circuit 111 controls an
in-viewfinder LCD 41 which is specifically shown in FIG. 2 and a
monitoring LCD 42 which is not shown in FIG. 2, in accordance with
a signal from the camera microcomputer 100.
[0107] The arrangement of the lens barrel 11 will be described
below. The camera body 1 and the lens barrel 11 are electrically
connected to each other via the mount contact group 10. The mount
contact group 10 includes a power supply contact L0 for the
focusing (first lens group) driving motor 16 and the lens diaphragm
driving motor 17 both of which are provided in the lens barrel 11,
a power supply contact L1 for the lens microcomputer 112, a
clock-signal contact L2 for communication of known serial data, a
contact L3 for transmission of data from the camera body 1 to the
lens barrel 11, a contact L4 for transmission of data from the lens
barrel 11 to the camera body 1, a motor grounding contact L5 for a
motor power supply, and a grounding contact L6 for a power supply
of the lens microcomputer 112.
[0108] The lens microcomputer 112 is connected to the camera
microcomputer 100 via the mount contact group 10, and operates the
first lens group driving motor 16 and the lens diaphragm driving
motor 17 to control a focus adjusting operation and the
photographing lens diaphragm 15 of the lens barrel 11. The lens
microcomputer 112 can obtain information indicative of the position
of the first lens group 12 and performing focus adjustment of the
lens barrel 11 or transmitting information indicative of the
absolute position of a subject to the camera microcomputer 100, by
counting the angle of rotation (the number of pulses) of a pulse
plate 36 through an optical detector 35.
[0109] The arrangement of the flash unit 18 will be described
below. The flash-unit microcomputer 200 is a circuit which performs
control of the flash unit 18 in accordance with a signal from the
camera microcomputer 100, and performs various kinds of control,
such as control of the amount of emission, control of the emission
intensity and the emission time of a flat emission, and control of
the illuminating angle of an emission.
[0110] A DC/DC converter 201 boosts a battery voltage to several
hundred volts and charges a main capacitor C1, in accordance with
an instruction given by the flash-unit microcomputer 200.
[0111] Voltage dividing resistors R1 and R2 are provided so that
the flash-unit microcomputer 200 can monitor the voltage of the
main capacitor C1. The flash-unit microcomputer 200 performs A/D
conversion of a divided voltage supplied from the resistors R1 and
R2, through an A/D converter (not shown) built in the flash-unit
microcomputer 200, and indirectly monitors the voltage of the main
capacitor C1 to control the operation of the DC/DC converter 201
and control the voltage of the main capacitor C1 to set it to a
predetermined voltage.
[0112] A trigger circuit 202 outputs a trigger signal in response
to an instruction or the signal SWX received from the camera
microcomputer 100 via the flash-unit microcomputer 200 during an
emission of the flash unit 18, and applies a high voltage of
several thousand volts to a trigger electrode of the xenon tube 19
to induce an electric discharge of the xenon tube 19. Thus, the
charge energy stored in the main capacitor C1 is discharged via the
xenon tube 19 as light energy.
[0113] An emission control circuit 203 employs a switching element
such as an IGBT. When a trigger voltage for starting an emission is
applied to the emission control circuit 203, the emission control
circuit 203 becomes conductive and allows a current to flow through
the xenon tube 19. When the emission control circuit 203 becomes
nonconductive and shuts off the flow of a current through the xenon
tube 19, the emission of the xenon tube 19 is made to stop.
[0114] A comparator 204 is employed for stopping an emission at the
time of the flash emission which will be described later, while a
comparator 205 is employed for controlling an emission intensity at
the time of the flat emission which will be described later. A data
selector 206 selects an input provided at any of terminals D0 to
D2, in accordance with selecting signals SEL0 and SEL1 supplied
from the flash-unit microcomputer 200, and outputs the selected
input to a terminal Y.
[0115] A flash-emission controlling monitor circuit 207
logarithmically compresses and amplifies the output of the monitor
sensor 31. An integrating circuit 208 integrates the output of the
flash-emission controlling monitor circuit 207. A flat-emission
controlling monitor circuit 209 amplifies the output of the monitor
sensor 32. A memory 210 is a writable memory, such as an EEPROM or
a flash ROM, for memorizing an emission time of the flat emission
and the like.
[0116] The flash unit 18 also includes a known motor driving
circuit 211, a flash zoom driving motor 212, a pinion gear 213, a
rack gear 214, a flash zoom position detecting encoder 215 for
detecting the position of the reflector 20 with respect to the
Fresnel lens 21, and an LED 216 for indicating whether an emission
is possible.
[0117] The flash unit 18 also includes a transmitting/receiving
circuit 217, a receiving sensor 218 and a transmitting infrared LED
219.
[0118] A switch SWB is a bounce detecting switch for detecting
whether the flash unit 18 is in a bounce state.
[0119] Each terminal of the flash-unit microcomputer 200 will be
described below. The flash-unit microcomputer 200 includes an input
terminal CK through which to input a synchronizing clock signal
required for the flash-unit microcomputer 200 to perform serial
communication with the camera body 1, an input terminal DI through
which to input serial communication data, an output terminal DO
through which to output serial communication data, an output
terminal CHG through which to transmit an emission-possible or
emission-impossible state of the flash unit 18 to the camera body 1
by means of an electric current, and an input terminal X through
which to input an emission signal from the camera body 1.
[0120] The flash-unit microcomputer 200 also includes an output
terminal ECK through which to output a communication clock signal
required for the flash-unit microcomputer 200 to perform serial
communication with a memory 210 externally connected to the
flash-unit microcomputer 200, an input terminal EDI through which
to input serial data from the memory 210, an output terminal EDO
through which to output serial data to the memory 210, and an
enable terminal SELE through which to output a signal which enables
or disables communication with the memory 210. If a low-level
signal is outputted through the enable terminal SELE, the
communication with the memory 210 is set to an enabled state,
whereas if a high-level is outputted through the enable terminal
SELE, the communication with the memory 210 is set to a disabled
state.
[0121] Although in this embodiment the memory 210 is provided
outside the flash-unit microcomputer 200, the memory 210 may be
built in the flash-unit microcomputer 200.
[0122] The flash-unit microcomputer 200 also includes an input
terminal POW through which to input a state of a power switch 220,
an output terminal OFF through which to output a signal to turn off
the flash unit 18, when connected to the power switch 220, and an
output terminal ON through which to output a signal to turn on the
flash unit 18, when connected to the power switch 220. If the power
switch 220 is turned on, the input terminal POW is connected to the
output terminal ON, and the impedance at the output terminal ON
becomes high while the impedance at the output terminal OFF becomes
low. If the power switch 220 is turned off, the input terminal POW
is connected to the output terminal OFF, and the impedance at the
output terminal ON becomes low while the impedance at the output
terminal OFF becomes high.
[0123] The flash-unit microcomputer 200 also includes a display
output terminal LED for providing a display indicating that an
emission is-possible, an input terminal IDI through which to input
data when the flash-unit microcomputer 200 communicates with the
camera body 1 by infrared light, and an output terminal IDO through
which to output serial data when the flash-unit microcomputer 200
communicates with the camera body 1 by infrared light.
[0124] The flash-unit microcomputer 200 also includes an input
terminal STOP through which to input an emission stop signal. If a
low-level signal is inputted through the input terminal STOP, the
flash-unit microcomputer 200 stops an emission of the flash unit
18. The flash-unit microcomputer 200 also includes output terminals
SEL0 and SEL1 for instructing the data selector 206 to select a
particular input from among the inputs D0 to D2. If low-level
signals are outputted from the respective output terminals SEL0 and
SEL1, the terminal D0 is connected to a terminal Y; if low- and
high-level signals are outputted from the respective output
terminals SEL0 and SEL1, the terminal D1 is connected to the
terminal Y; and if high- and low-level signals are outputted from
the respective output terminals SEL0 and SEL1, the terminal D2 is
connected to the terminal Y.
[0125] A terminal DAO is the output terminal of a D/A converter
built in the flash-unit microcomputer 200, and a comparison level
for each of the comparators 204 and 205 is outputted from the
output terminal DAO. A terminal TRIG is an output terminal through
which to output a trigger signal which instructs the trigger
circuit 202 to trigger an emission. A terminal CNT is an output
terminal through which to output a signal for controlling the
operation of the DC/DC converter 201 to start and stop charging the
main capacitor C1. If a high-level signal is outputted from the
output terminal CNT, the DC/DC converter 201 starts charging the
main capacitor C1, and if a low-level signal is outputted from the
output terminal CNT, the DC/DC converter 201 stops charging the
main capacitor C1.
[0126] A terminal INT is an output terminal through which to output
a signal for controlling the integration operation of the
integrating circuit 208. If a high-level signal is outputted from
the output terminal INT, the integrating circuit 208 is inhibited
from performing an integration, whereas if a low-level signal is
outputted from the output terminal INT, the integrating circuit 208
is enabled to perform an integration.
[0127] Terminals are A/D input terminals AD0 and AD1 through which
to input voltages to be converted into digital data so that they
can be processed in the flash-unit microcomputer 200. The input
terminal AD0 is provided for monitoring the voltage of the main
capacitor C1, while the input terminal AD1 is provided for
monitoring the integral output voltage of the integrating circuit
208.
[0128] The flash-unit microcomputer 200 also includes control
output terminals Z0 and Z1 through which to control the motor
driving circuit 211 for driving the flash zoom driving motor 212,
input terminals ZM0, ZM1 and ZM2 through which to input signals
outputted from the flash zoom position detecting encoder 215, and a
common terminal COMO through which to input a current equivalent to
the ground level of the flash zoom position detecting encoder
215.
[0129] A terminal BOUNCE is an input terminal through which to
input a signal (supplied from the switch SWB) indicating whether
the flash unit 18 is in a bounce state.
[0130] Individual operations of the flash unit 18 as well as the
operation of the circuit shown in FIG. 4 will be described
below.
Detection of Whether Emission is Possible
[0131] The flash-unit microcomputer 200 performs A/D conversion of
a divided voltage of the main capacitor C1 which has been inputted
through the terminal AD0. If the flash-unit microcomputer 200
determines that the voltage of the main capacitor C1 is not less
than a predetermined voltage at which an emission is possible, the
flash-unit microcomputer 200 draws a predetermined current through
the terminal CHG to inform the camera body 1 that an emission is
possible, and sets a high-level signal at the terminal LED. Thus,
the LED 216 emits light to provide a display indicating that the
emission of the flash unit 18 is possible.
[0132] If the flash-unit microcomputer 200 determines that the
voltage of the main capacitor C1 is less than the predetermined
voltage, the flash-unit microcomputer 200 makes the terminal CHG
inactive and shuts off the flow of the predetermined current to
inform the camera body 1 that an emission is impossible, and sets a
low-level signal at the terminal LED. Thus, the LED 216 is turned
off to provide a display indicating that the emission of the flash
unit 18 is impossible.
Setting of Illuminating Angle of Flash Unit
[0133] The flash-unit microcomputer 200 reads the current flash
zoom position through the terminals ZM0 to ZM2, and outputs
predetermined signals to the motor driving circuit 211 through the
terminals Z0 and Z1 and drive the flash zoom driving motor 212 so
that the flash zoom position can be set to a flash zoom position
specified by the camera microcomputer 100 through a serial
communication.
Preliminary Flat Emission
[0134] If the flash unit 18 is in the emission-possible state, the
camera microcomputer 100 communicates the emission intensity and
the emission time of a preliminary emission to the flash unit 18,
and can instruct the flash unit 18 to execute the preliminary
emission.
[0135] The flash-unit microcomputer 200 sets a predetermined
voltage at the terminal DAO according to a predetermined emission
intensity signal transmitted from the camera microcomputer 100, and
then sets low- and high-level signals at the respective terminals
SEL0 and SEL1 to select the terminal D1. At this time, since the
xenon tube 19 has not yet emitted light, a substantial amount of
photoelectric current does not flow in the monitor sensor 32 and
the monitor circuit 209 does not output a signal to be applied to
the inverting input terminal of the comparator 205, so that the
output of the comparator 205 goes to its high level and the
emission control circuit 203 is brought to a conductive state. When
a trigger signal is outputted from the terminal TRIG, the trigger
circuit 202 generates a high voltage to discharge the xenon tube
19, so that an emission (preliminary emission) of the flash unit 18
is started.
[0136] In the meantime, when a predetermined time passes after the
trigger circuit 202 has generated the trigger signal, the
flash-unit microcomputer 200 instructs the integrating circuit 208
to start an integration, so that the integrating circuit 208 starts
to integrate the output of the monitor circuit 207, i.e., a
logarithmically compressed photoelectric output of the monitor
sensor 31 for integrating the amount of light. At the same time,
the flash-unit microcomputer 200 activates a timer for counting a
predetermined time.
[0137] When the preliminary emission is started, the amount of
photoelectric current in the monitor sensor 32 for controlling the
emission intensity of the flat emission increases and the output
voltage of the flat-emission controlling monitor circuit 209 rises.
When this output voltage becomes higher than a predetermined
comparison voltage which is set at the non-inverting input terminal
of the comparator 205, the output of the comparator 205 is inverted
from high to low and the emission control circuit 203 shuts off the
emission current of the xenon tube 19. Thus, the discharge loop of
the xenon tube 19 is shut down, but since a circulating current
loop is formed by a diode DD1 and a coil L1, the emission current
gradually decreases after an overshoot due to a circuit delay has
subsided.
[0138] Since the emission intensity falls with the decrease in the
emission current, the photoelectric current of the monitor sensor
32 decreases and the output of the monitor circuit 209 falls. If
this output falls below the predetermined comparison level, the
output of the comparator 205 is again inverted from low to high and
the emission control circuit 203 becomes conductive to form the
discharge loop of the xenon tube 19, so that the emission current
increases and the emission intensity also increases. In this
manner, the output level of the comparator 205 is repeatedly
inverted on the basis of the predetermined comparison voltage set
at the terminal DAO to cause the emission intensity to repeatedly
increase and decrease at intervals of a short period, so that the
control of the flat emission of continuing an emission at a desired
approximately constant emission intensity is effected.
[0139] The peak value of the flat emission can be controlled to
become a desired value, by the processing of varying a digital
value for setting a voltage at the terminal DAO, varying the
comparison voltage to be applied to the non-inverting input
terminal of the comparator 205, and varying the operating point of
the photoelectric current of the monitor sensor (PD2) 32.
[0140] When the aforesaid emission time timer counts up and a
predetermined preliminary emission time passes, the flash-unit
microcomputer 200 sets low- and low-level signals at the respective
terminals SEL1 and SEL2. Thus, the data selector 206 selects the
input D0, i.e., the low-level input, and the output of the data
selector 206 forcedly goes to its low level, so that the emission
control circuit 203 shuts off the discharge loop of the xenon tube
19 and brings the preliminary emission to an end.
[0141] At the time of the end of the preliminary emission, the
flash-unit microcomputer 200 reads through the input terminal AD1
the integral output of the integrating circuit 208 in which an
integration of the preliminary emission has been performed, and
performs A/D conversion of the read integral output and obtains an
integral value, i.e., the amount of emission of the preliminary
emission, as a digital value "INTp".
[0142] A guide number "Qpre" of the preliminary emission pointed at
a particular subject is obtained from the charged voltage of the
main capacitor C1 and the illuminating angle of the flash unit 18,
as shown in Table 1, and the obtained data is sent to the camera
microcomputer 100 by serial communication.
1TABLE 1 (Preliminary Emission Guide Number) CHARGED AMOUNT OF LENS
AMOUNT OF VOLTAGE CORRECTION FOCAL CORRECTION [V] [EV] LENGTH [EV]
250 -0.80 24 mm +0.5 260 -0.68 28 mm +0.4 270 -0.57 35 mm +0.3 280
-0.47 50 mm +0.2 290 -0.37 70 mm +0.1 300 -0.28 105 mm 0.0 310
-0.18 320 -0.09 330 0.00
[0143] Since the above data for the guide number "Qpre" are
theoretical values, they may be corrected on the basis of a value
which is obtained by actually measuring the integral value of a
preliminary emission by means of the monitor circuit 207 and the
integrating circuit 208.
Main Emission Control
[0144] The camera microcomputer 100 obtains a correct relative
value "r" of the amount of emission of a main emission with respect
to the amount of emission of a preliminary emission, from a
luminance value of subject-reflected light or the like which is
supplied from the multiple divided weight measuring sensor 7 during
the preliminary emission. The camera microcomputer 100 sends the
correct relative value "r" to the flash-unit microcomputer 200.
[0145] The flash-unit microcomputer 200 obtains a correct integral
value "INTm" by multiplying the correct relative value "r" sent
from the camera microcomputer 100 by an integral value "INTp" of
the measured light value of the preliminary emission, and sets the
correct integral value "INTm" at the output terminal DAO.
[0146] Then, the flash-unit microcomputer 200 sets high- and
low-level signals at the respective terminals SELL and SEL2 to
select the terminal D2. At this time, since the integrating circuit
208 is placed in an operation-inhibited state, the integrating
circuit 208 does not provide any output. Therefore, the output of
the comparator 204 goes to a high level and the emission control
circuit 203 becomes conductive.
[0147] Then, when the flash-unit microcomputer 200 outputs a
trigger signal from the terminal TRIG, the xenon tube 19 starts to
emit light. The flash-unit microcomputer 200 sets a low-level
signal at the integration start terminal INT when an actual
emission is started more than 10 .mu.sec after trigger noise due to
the application of the trigger signal has been settled. Thus, the
integrating circuit 208 integrates the output from the monitor
sensor 31 via the monitor circuit 207. When the integral output of
the integrating circuit 208 reaches the predetermined voltage set
at the terminal DAO, the comparator 204 is inverted and the
conduction of the emission control circuit 203 is shut off via the
data selector 206 to stop the emission of the xenon tube 19.
[0148] In the meantime, the flash-unit microcomputer 200 monitors
the state of the input terminal STOP. When the input level at the
input terminal STOP is inverted and the emission is stopped, the
flash-unit microcomputer 200 sets low- and low-level signals at the
terminals SEL1 and SEL2 to set a forcedly emission-inhibited state.
In addition, the flash-unit microcomputer 200 inverts the level at
the integration start terminal INT to bring the integration as well
as the entire emission processing to an end. In the above-described
manner, the main emission can be controlled to provide a correct
amount of emission.
[0149] The operation flow of the present camera system will be
described below with reference to FIGS. 5 to 8, and the following
description is mainly focused on the operation of the camera
microcomputer 100. The flows of FIGS. 5 and 6 are joined at the
circled letter "A". When the operation of the camera system is
started, the process proceeds to Step S101, in which the camera
microcomputer 100 determines whether the switch SW1 is on. If the
switch SW1 is off, Step S101 is repeated. If the switch SW1 is on,
the process proceeds to Step S102.
[0150] In Step S102, the camera microcomputer 100 reads from the
switch sense circuit 110 the states of individual operating
switches (not shown) of the camera system, and sets various
photographing modes, such as a method of determining a shutter
speed and a method of determining an aperture value.
[0151] Then, in Step S103, the camera microcomputer 100 determines
whether the photographing modes which have been set for the camera
system in Step S102 contain a mode for executing an automatic focus
detecting operation (AF mode) or another mode (MF mode). If the AF
mode has been selected, the camera microcomputer 100 processes
Steps S104 and S105 and then proceeds to Step S106. If the MF mode
has been selected, the camera microcomputer 100 proceeds to Step
S106.
[0152] In Step S104, the camera microcomputer 100 drives the focus
detecting circuit 105 to perform a focus detecting operation using
a known phase-difference detecting method. The camera microcomputer
100 further performs focus adjustment on the basis of the state of
the detected focus by performing communication with the lens barrel
11. In this embodiment, three points for focus detection are
provided on the image plane, as described previously with reference
to FIG. 2. Which of the three points at which subjects are
respectively present is to be focused (a distance measuring point)
is determined according to the photographing modes which have been
set for the camera system on the basis of the aforesaid read states
of individual operating switches. For example, the distance
measuring point may be arbitrarily determined by the photographer,
or may be determined by finding the amounts of defocusing at the
respective points and executing a known automatic selection
algorithm based on the concept of nearest-point priority (the
algorithm of selecting the nearest point from all the points on the
basis of the respective amounts of defocusing and focusing a
subject lying at the nearest point).
[0153] In Step S105, the distance measuring point determined in
Step S104 is memorized as "Focus.P" in a RAM (random access memory)
provided in the camera microcomputer 100.
[0154] In Step S106, the camera microcomputer 100 obtains the
subject luminance values of the respective six areas provided in
the image plane, through the light measuring circuit 106. The
subject luminance values are memorized in the RAM as EVb(i) (i=0-5)
(i indicates numbers which correspond to the respective areas E0 to
E5, and (Ei) and EVb(i) indicates the luminance values of the
respective areas E0 to E5 (Ei)).
[0155] Then, in Step S107, the camera microcomputer 100 determines
an exposure value "EVs" from the subject luminance values EVb of
the respective six areas by a known algorithm (for example,
center-weighted average light measurement). Then, the camera
microcomputer 100 determines the value of a shutter speed "TV" and
the value of an aperture "AV" in accordance with the photographing
modes which have been set for the camera system on the basis of the
aforesaid read states of the individual operating switches.
Incidentally, this Evs is a value determined according to TV and AV
which are actually controlled during flash photography, and may not
be determined according to EVb.
[0156] Then, in Step S108, the camera microcomputer 100
communicates data with the lens microcomputer 112 and receives
information about the photographing lens system, such as:
[0157] focal length "f",
[0158] minimum value of distance to subject "Dist_min", and
[0159] maximum value of distance to subject "Dist_max". The reason
why two kinds of values of the distance to a subject, the minimum
and maximum values, are prepared is that the resolution of distance
information relative to the distance between the photographing lens
system and the subject is low. For example, if the minimum and
maximum values indicate that the distance ring of the photographing
lens system is located within the range of 1 m to 1.5 m, the data
of the minimum value is 1 m and the data of the maximum value is
1.5 mm. To obtain such data, a position encoder may be provided in
the lens barrel 11.
[0160] Then, in Step S109, the camera microcomputer 100 transmits
the focal length information "f" and the like to the flash unit 18.
The flash-unit microcomputer 200 drives the motor driving circuit
211 on the basis of the focal length information "f", and controls
the illuminating angle of the flash unit 18.
[0161] Then, in Step S110, the camera microcomputer 100 determines
whether the switch SW2 is on, and if the switch SW2 is off, the
camera microcomputer 100 repeats the operation of Steps S101 to
S110, whereas if the switch SW2 is on, the process proceeds to a
shutter release operation which starts with Step S111.
[0162] In Step S111, the camera microcomputer 100 obtains a subject
luminance immediately before the preliminary emission through the
light measuring circuit 106. The obtained subject luminance value
is memorized in the RAM as EVa (i) (i=005).
[0163] In Step S112, the camera microcomputer 100 transmits to the
flash unit 18 an instruction to execute the preliminary emission.
The flash-unit microcomputer 200 performs the preliminary emission
operation in the above-described manner in accordance with the
instruction. Then, in Step S113, while the flat emission of the
preliminary emission is being sustained, the camera microcomputer
100 obtains a subject luminance through the light measuring circuit
106. The obtained subject luminance value is memorized in the RAM
as Evf (i) (i=0-5).
[0164] Then, in Step S114, the camera microcomputer 100 moves up
the main mirror 2 and retracts the main mirror 2 from the
photographic optical path together with the sub-mirror 25, prior to
an exposure operation.
[0165] Then, in Step S115, the camera microcomputer 100 expands
into antilogarithms the subject luminance value Evf obtained in
Step S113 during the sustaining of the flat emission of the
preliminary emission and the subject luminance number Eva obtained
in Step S111 immediately before the preliminary emission, and then
finds the difference between the antilogarithms, thereby extracting
the luminance value EVdf(i) of only a preliminary-emission
reflected light component:
EVdf(i).rarw.LN.sub.2(2.sup.EVf(i)-2.sup.EVa(i))
[0166] (i=0-5)
[0167] Then, in Step S116, the camera microcomputer 100 receives
the following kinds of data from the flash unit 18:
[0168] preliminary emission guide number "Qpre", and
[0169] bounce flag "F_Bounce".
[0170] The preliminary emission guide number "Qpre" is a value
which is obtained from the focal length information "f" of the
photographing lens system, the charged voltage of the main
capacitor C1 and the like by the flash-unit microcomputer 200. The
bounce flag "F_Bounce" is a flag which is sent by the flash-unit
microcomputer 200 on the basis of the terminal BOUNCE.
[0171] Then, in Step S117, the camera microcomputer 100 determines
which of the six divided light measuring areas the amount of flash
light is to be correctly adjusted to, on the basis of a distance
measuring point "Focus.P", the focal length "f", the amount of
emission of the preliminary emission "Qpre", the bounce flag
"F_Bounce" and the like. The camera microcomputer 100 memorizes the
selected light measuring area in the RAM as P (any one of P0-P5).
Step S117 will be described later in more detail.
[0172] Then, in Step S118, the camera microcomputer 100 determines
whether an appropriate subject is present in the selected area P,
with reference to the focal length information "f", the subject
distance information "Dist" and the like. If it is determined that
the subject is an abnormal reflective subject, the camera
microcomputer 100 corrects the amount of emission of the main
emission. The amount of emission of the main emission is corrected
by correcting a luminance value EVdf(p) of only the
preliminary-emission reflected light component and causing a
relative ratio "r" of the amount of emission of the main emission
to the amount of emission of the preliminary emission to correspond
to a corrected luminance value EVdf(p), the relative ratio "r"
being computed in the next step S119. This part will be described
later in more detail.
[0173] Then, in Step S119, the camera microcomputer 100 obtains the
relative ratio of the amount of correct emission of the main
emission to the amount of emission of the preliminary emission with
respect to the subject present in the selected area "P", from the
exposure value "EVs" and the subject luminance "EVb" and the
luminance value EVdf(p) of only the preliminary-emission reflected
light component, by using the following expression:
r.rarw.LN.sub.2(2.sup.EVs-2.sup.EVb(p))-EVdf(p)
[0174] The reason why the camera microcomputer 100 obtains, in this
step, the difference between the antilogarithms into which the
exposure value "EVs" and the subject luminance "EVb" have been
expanded (the amount of underexposure due to external light) is
that the flash unit 18 needs to be controlled so that when a
subject is illuminated with flash light, the subject can be
correctly exposed to both external light and the flash light. In
other words, the camera microcomputer 100 finds how many times (r
times) as intensive as the preliminary flat emission the main
emission needs to be made in order to compensate for the amount of
underexposure due to the external light by using the luminance
EVdf(p) due to the preliminary flat emission.
[0175] Then, in Step S120, the camera microcomputer 100 corrects
the relative ratio "r", as expressed by the following expression,
by using the shutter speed "TV", an emission time "t_pre" of the
preliminary emission and a correction coefficient "c" which is set,
as by the photographer, and computes a new relative ratio "r":
r.rarw.r+TV-t_pre+c
[0176] where each variable is a compression variable.
[0177] The reason why the camera microcomputer 100 corrects the
relative ratio "r" by using the shutter speed "TV" and the emission
time "t_pre" of the preliminary emission is that it is necessary to
correctly compare, within the flash unit 18, the measured light
integral value "INTp" of the amount of emission of the preliminary
emission and the measured light integral value "INTm" of the main
emission.
[0178] Then, in Step S121, the camera microcomputer 100 transmits
to the flash unit 18 the relative ratio "r" of the amount of
emission required to determine the amount of emission of the main
emission. Then, in Step S122, the camera microcomputer 100 gives
the lens microcomputer 112 an instruction to find an aperture value
"AV" based on the determined exposure value "EVs", and causes the
shutter control circuit 107 to control the shutter 8 so that the
determined shutter speed "TV" is achieved.
[0179] Then, when the switch SWX is turned on in synchronism with
the timing at which the shutter 8 is fully opened (Step S123), the
signal SWX is transmitted to the flash-unit microcomputer 200 as an
instruction to execute the main emission. The flash-unit
microcomputer 200 performs main-emission control so that a correct
amount of emission can be achieved, on the basis of the relative
ratio "r" sent from the camera body 1.
[0180] When one exposure cycle is completed in the above-described
manner, the process proceeds to Step S124, in which the camera
microcomputer 100 moves down the main mirror 2 and the like which
have been retracted from the photographing optical path, thereby
again obliquely inserting the main mirror 2 and the like into the
photographing optical path. The camera microcomputer 100 winds the
film 9 by one frame, by means of the motor control circuit 108 and
the film running detecting circuit 109.
[0181] The subject-area selecting routine executed in the
aforementioned step S117 will be described below with reference to
FIG. 7. First of all, in Step S201, the camera microcomputer 100
determines whether the camera system is in the AF mode or the MF
mode. If the AF mode has been selected, the process proceeds to
Step S205, whereas if the MF mode has been selected, the process
proceeds to Steps S202 to S204.
[0182] In Step S202, the camera microcomputer 100 determines
whether the value of the bounce flag "F_Bounce" sent from the flash
unit 18 in Step S116 is "1" or "0". If the value is "1", the camera
microcomputer 100 determines that the flash unit 18 is in the
bounce state, and proceeds to Step S211 without executing Steps
S203 and S204 and selects a subject area to which to correctly
adjust the amount of emission, without taking account of the focal
length information "f". Specifically, if the flash unit 18 is in
the bounce state, this indicates that the preliminary emission does
not directly reach a subject, so that neither of the decisions of
Steps S203 and S204 can be executed. For this reason, in Step S211,
the light measuring area "Focus.P" which contains a distance
measuring point is selected as an area to be used for computing the
amount of correct emission of the main emission, and the camera
microcomputer 100 brings this routine to an end.
[0183] If the value of the bounce flag "F_Bounce" is "0", the
process proceeds to Steps S203 and S204, in which the camera
microcomputer 100 selects a light measuring area in the following
sequence while taking account of the focal length information
"f".
[0184] In Step S203, the camera microcomputer 100 obtains the
preliminary-emission reflected light component "EVdf" at a most
distant position beyond which a subject such as a person becomes
excessively small with respect to one light measuring area, from
the focal length information "f", the amount of emission of the
preliminary emission "Qpre" and a predetermined coefficient "c1",
and sets the obtained reflected light component as "level.1".
[0185] This step will be described below with reference to FIGS.
10(a) and 10(b). If a person is large with respect to one light
measuring area as shown in FIG. 10(a), the preliminary-emission
reflected light component "EVdf" can be accurately measured through
that area. However, if a person is small with respect to one light
measuring area as shown in FIG. 10(b), part of the light of the
preliminary emission passes the person and all the light does not
return to the light measuring area, so that the value of the
preliminary-emission reflected light component "EVdf" becomes lower
than when a gray wall of standard reflectance is present at the
position of the person. For this reason, in the case shown in FIG.
10(b), if the amount of emission of the main emission relative
ratio "r") is computed by using the preliminary-emission reflected
light component "EVdf" on an "as-measured" basis, the amount of
emission of the main emission becomes excessively large and
overexposure occurs.
[0186] To cope with this problem, a threshold level beyond which
overexposure occurs is set as "level.1". This "level.1" employs,
for example, the value of the preliminary-emission reflected light
component "EVdf" which is obtained when a gray wall of standard
reflectance is present at a position which is approximately 3 mm
away from a lens having a focal length of 50 mm.
[0187] In Step S204, the camera microcomputer 100 determines
whether the preliminary-emission reflected light component
"EVdf(Focus.P)" obtained at a light measuring point is not less
than the aforesaid "level.1". If the preliminary-emission reflected
light component "EVdf(Focus.P)" obtained at the light measuring
point is not less than "level.1", the process proceeds to Step
S211. If the preliminary-emission reflected light component
"EVdf(Focus.P)" which is obtained at the light measuring point is
not less than "level.1", this indicates that a subject such as a
person is sufficiently large with respect to a light measuring area
which contains the light measuring point, and that the
preliminary-emission reflected light component "EVdf" has been
accurately measured. Therefore, the light measuring area "Focus.P"
which contains the light measuring point is selected as an area to
be used for computing the amount of correct emission of the main
emission, and the process brings this routine to an end.
[0188] On the other hand, if the preliminary-emission reflected
light component "EVdf(Focus.P)" obtained at the light measuring
point is less than "level.1", the process proceeds to Step
S205.
[0189] If it is determined in Step S201 that the MF mode is
selected and it is determined in Step S204 that the
preliminary-emission reflected light component "EVdf(Focus.P)" is
less than "level.1" and the light measuring area which contains the
light measuring point cannot be selected as an area to be used for
computing the amount of correct emission of the main emission, the
process proceeds to Step S205. In Step S205, the camera
microcomputer 100 selects an area "Close.P" in which a subject
nearest to the camera system is present, from the central three
light measuring areas E0, E1 and E2. This selection method is based
on the concept that there is a highest possibility that a subject
which is nearest to the camera system of all the subjects in the
image plane is a main subject. Specifically, a light measuring area
in which the preliminary-emission reflected light component
"EVdf(i)" reaches a maximum is set to the area "Close.P".
[0190] Then, in Step S206, the camera microcomputer 100 determines
whether the value of the bounce flag "F_Bounce" which has been sent
from the flash unit 18 in Step S116 is "0" or "1". If the value is
"1", the camera microcomputer 100 determines that the flash unit 18
is in the bounce state, and proceeds to Step S212 without executing
Steps S207 and S208 and selects a light measuring area to which to
correctly adjust the amount of emission of the main emission,
without taking account of the focal length information "f".
Specifically, if the flash unit 18 is in the bounce state, this
indicates that the preliminary emission does not directly reach a
subject, so that neither of the decisions of Steps S207 and S208
can be executed. For this reason, the light measuring area
"Focus.P" which contains a closest-distance point is selected as an
area to be used for computing the amount of correct emission of the
main emission, and the camera microcomputer 100 brings this routine
to an end.
[0191] On the other hand, if the value of the bounce flag
"F_Bounce" is "0", the process proceeds to Steps S207 and S208 and
the camera microcomputer 100 selects a light measuring area while
taking account of the focal length information "f".
[0192] In Step S207, the camera microcomputer 100 obtains the
preliminary-emission reflected light component "EVdf" at a most
distant position beyond which a subject such as a person becomes
excessively small with respect to one light measuring area, from
the focal length information "f", the amount of emission of the
preliminary emission "Qpre" and a predetermined coefficient "c2",
and sets the obtained reflected light component as "level.2".
[0193] Although "level.2" is set in a manner similar to that used
for finding "level.1" in Step S203, the value of "level.2" is set
higher than that of "level.1" on the basis of the concept of
weighting the light measuring point to a further extent. For this
reason, even if a subject such as a person lies considerably near
the camera system and a large amount of light of the preliminary
emission does not pass the subject, the preliminary-emission
reflected light component becomes less than that "level.2". This
"level.2" employs, for example, the value of the
preliminary-emission reflected light component "EVdf" which is
obtained when a gray wall of standard reflectance is present at a
position which is approximately 2.5 mm away from a lens having a
focal length of 50 mm.
[0194] Then, in Step S208, the camera microcomputer 100 determines
whether the preliminary-emission reflected light component
"EVdf(Close.P)" obtained at the closest-distance point is not less
than the aforesaid "level.2". If the reflected light component
"EVdf(Close.P)" is not less than "level.2", this indicates that a
subject such as a person is sufficiently large with respect to a
light measuring area which contains the closest-distance point, and
that the preliminary-emission reflected light component "EVdf" has
been accurately measured. Therefore, the light measuring area
"Close.P" which contains the closest-distance point is selected as
an area to be used for computing the amount of correct emission of
the main emission, and the process brings this routine to an
end.
[0195] On the other hand, if the preliminary-emission reflected
light component "EVdf(Close.P)" obtained at the closest-distance
point is less than "level.2", the process proceeds to Step S209. If
the preliminary-emission reflected light component "EVdf(Close.P)"
obtained at the closest-distance point is less than "level.2", this
indicates that a subject such as a person is present at a position
considerably away from the camera system or in a peripheral portion
of the image plane. Accordingly, in Step S209, the camera
microcomputer 100 selects a light measuring area to be used for
computing the amount of correct emission of the main emission,
while taking account of not only the central three areas E0, E1 and
E2 but also the peripheral areas E3 and E4.
[0196] Step S209 will be described below with reference to FIG. 9.
First, in Step S401, 3 is substituted for a variable i, and in Step
S402, a preliminary-emission reflected light component "EVdf(3)"
relative to the area E3 is compared with the aforesaid "level.2".
If the preliminary-emission reflected light component "EVdf(3)" is
less than the aforesaid "level.2", the process proceeds to Step
S403, in which the preliminary-emission reflected light component
"EVdf(i)" is corrected to obtain:
EVdf(i).rarw.(EVdf(i)+level.2)/2
[0197] The processing of Step S403 is based on the concept that
when the amount of emission of the main emission is to be computed
on the basis the preliminary-emission reflected light component
"EVdf" relative to the peripheral area E3 adjacent to the area E0
as shown in FIG. 10(b), the preliminary-emission reflected light
component "EVdf" is corrected to become a large value, because the
preliminary-emission reflected light component "EVdf" obtained when
light measurement is performed on the area E3 with a subject
considerably small with respect to the area E3 as shown in FIG.
10(b) is small compared to a gray wall of standard reflectance.
[0198] On the other hand, if the preliminary-emission reflected
light component "EVdf(3)" is not less than the aforesaid "level.2",
the process proceeds to Step S404, in which the
preliminary-emission reflected light component "EVdf(i)" is
corrected to obtain:
EVdf(i).rarw.level.2
[0199] The processing of Step S404 is based on the concept that
since the preliminary-emission reflected light component "EVdf" is
in many cases considerably large in a peripheral area such as the
peripheral area E3 if an obstacle such as a table is placed in
front of a main subject, the preliminary-emission reflected light
component "EVdf" obtained by the light measurement is corrected to
become a small value so that the main subject is prevented from
being underexposed by the amount of exposure being adjusted to the
obstacle.
[0200] The process proceeds to Step S403 or S404 to Step S405, in
which the variable i is incremented by one. Since the current
variable "i" is "3", the variable "i" is made "4". Then, in Step
S406, the camera microcomputer 100 determines whether the variable
"i" is not greater than "4". If the variable "i", is not greater
than "4", Steps S402 to S405 are repeated. After that, the variable
"i" is incremented to "5" and if it is determined in Step S406 that
the variable "i" is greater than "4", the camera microcomputer 100
brings this routine to an end.
[0201] In Step S210 of FIG. 7, the camera microcomputer 100 selects
a light measuring area having the maximum preliminary-emission
reflected light component from the preliminary-emission reflected
light component "EVdf(Close.P)" relative to the one of the central
three light measuring areas which contains the closest-distance
point and the corrected preliminary-emission reflected light
component "EVdf" relative to the area E3 or E4,which has been
calculated in Step S209 (S401-S406), and sets the selected light
measuring area as an area to be used for computing the amount of
correct emission of the main emission and brings this routine to an
end.
[0202] The abnormal-reflection correcting routine of the
aforementioned Step S118 will be described below with reference to
FIG. 8. In Step S301, the camera microcomputer 100 determines
whether the value of the bounce flag "F_Bounce" sent from the flash
unit 18 in Step S116 is "0" or "1". If the value is "1", this
indicates that the flash unit 18 is in the bounce state, and the
camera microcomputer 100 immediately brings this routine to an end
without executing correction of abnormal reflection.
[0203] On the other hand, if the value of the bounce flag
"F_Bounce" is "0", the process proceeds to Step S302 and executes
correction of abnormal reflection. In Step S302, the camera
microcomputer 100 obtains the preliminary-emission reflected light
component "EVdf" at a position at which a subject such as a person
is substantially nearest to the camera system, from the focal
length information "f", the amount of emission of the preliminary
emission "Qpre" and a predetermined coefficient "c3", and sets the
obtained reflected light component as "level.3".
[0204] This "level.3" employs, for example, the value of the
preliminary-emission reflected light component "EVdf" which is
obtained when a gray wall of standard reflectance is present at a
position which is approximately 0.5 mm away from a lens having a
focal length of 50 mm. This is based on the concept that if a lens
having a focal length of 50 mm is used, a subject is not at all
present within the shortest photographing distance (approximately
0.5 m) of the lens.
[0205] In Step S303, the camera microcomputer 100 compares the
aforesaid "level.3" and the preliminary-emission reflected light
component "EVdf(P)" relative to the light measuring area selected
for computing the amount of correct emission of the main emission.
If the preliminary-emission reflected light component "EVdf(P)" is
not greater than "level.3", the camera microcomputer 100 brings
this routine to an end.
[0206] On the other hand, if the preliminary-emission reflected
light component "EVdf(P)" is greater than "level.3", the process
proceeds to Step S304, in which the camera microcomputer 100 sets
the preliminary-emission reflected light component "EVdf(P)" as
follows:
EVdf(P).rarw.level.3
[0207] and brings this routine to an end. By correcting the
preliminary-emission reflected light component "EVdf(P)" in this
manner, the amount of emission of the main emission is corrected so
that the amount of correction is effected at an underexposure
level.
[0208] As described above, according to the present embodiment, a
light measuring area to be used for correcting the amount of
emission of the main emission or for computing the amount of
emission of the main emission is selected according to whether the
flash unit 18 is in the bounce state, so that it is possible to
realize a camera system capable of providing a correct amount of
exposure at all times.
[0209] FIG. 11 shows another example of the abnormal-reflection
correcting routine shown in FIG. 8. In the routine shown in FIG.
11, "level.3.1" and "level.3.2" are obtained by using the minimum
value "Dist_min" and the maximum value "Dist_max" of the distance
to a subject, instead of "level.3" obtained by using the focal
length information "f" in the routine of FIG. 8.
[0210] First, in Step S501, the camera microcomputer 100 determines
whether the value of the bounce flag "F_Bounce" which has been sent
from the flash unit 18 in Step S116 is "0" or "1". If the value is
"1", this indicates that the flash unit 18 is in the bounce state,
so that the camera microcomputer 100 immediately brings this
routine to an end without executing correction of abnormal
reflection.
[0211] On the other hand, if the value of the bounce flag
"F_Bounce" is "0", the process proceeds to Step S502 and executes
correction of abnormal reflection.
[0212] In Step S502, the camera microcomputer 100 obtains the
preliminary-emission reflected light component "EVdf" at a position
at which a subject such as a person is substantially nearest to the
camera system, from the minimum subject distance information "Dist
min" which has been sent from the lens barrel 11 in Step S108, the
amount of emission of the preliminary emission "Qpre" and a
predetermined coefficient "c3.1", and sets the obtained reflected
light component as "level.3.1".
[0213] In Step S503, the camera microcomputer 100 compares the
aforesaid "level.3.1" and the preliminary-emission reflected light
component "EVdf(P)" relative to the light measuring area selected
for computing the amount of correct emission of the main emission.
If the preliminary-emission reflected light component "EVdf(P)" is
not greater than "level.3.1", the process proceeds to Step S504. On
the other hand, if the preliminary-emission reflected light
component "EVdf(P)" is greater than "level.3.1", the process
proceeds to Step S507, in which the camera microcomputer 100 sets
the preliminary-emission reflected light component "EVdf(P)" as
follows:
EVdf(P).rarw.level.3.1
[0214] and brings this routine to an end. In other words, by
computing the amount of emission of the main emission by using the
preliminary-emission reflected light component "EVdf(P)" corrected
in this manner, the amount of emission of the main emission is
corrected so that the main emission is effected at an underexposure
level.
[0215] In Step S504, the camera microcomputer 100 obtains the
preliminary-emission reflected light component "EVdf" at a position
at which a subject such as a person is most distant from the camera
system, from the maximum subject distance information "Dist_max"
which has been sent from the lens barrel 11 in Step S108, the
amount of emission of the preliminary emission "Qpre" and a
predetermined coefficient "c3.2", and sets the obtained reflected
light component as "level.3.2".
[0216] In Step S505, the camera microcomputer 100 compares the
aforesaid "level.3.2" and the preliminary-emission reflected light
component "EVdf(P)" relative to the light measuring area selected
for computing the amount of correct emission of the main emission.
If the preliminary-emission reflected light component "EVdf(P)" is
less than "level.3.2", the process proceeds to Step S506, in which
the camera microcomputer 100 sets the preliminary-emission
reflected light component "EVdf(P)" as follows:
EVdf(P).rarw.level.3.2
[0217] and brings this routine to an end. In other words, by
computing the amount of emission of the main emission by using the
preliminary-emission reflected light component "EVdf(P)" corrected
in this manner, the amount of emission of the main emission is
corrected so that the main emission is effected at an overexposure
level.
[0218] On the other hand, if the preliminary-emission reflected
light component "EVdf(P)" is not less than "level.3.2", the camera
microcomputer 100 determines that the distance range represented by
the maximum subject distance information "Dist_max", which has been
sent from the lens barrel 11, and the value of the
preliminary-emission reflected light component "EVdf(P)" correctly
agree with each other and there is no abnormality. Then, the camera
microcomputer 100 brings this routine to an end without executing
correction of abnormal reflection.
[0219] In this manner, in the routine shown in FIG. 11, since the
amount of emission of the main emission is corrected by using the
maximum and minimum values of the distance from the lens barrel 11
to a subject, it is possible to more accurately correct the amount
of emission of the main emission than when focal length information
is used, so that the amount of emission of the main emission is
prevented from being reduced to an underexposure level by abnormal
reflection such as the regular reflection of glass. In addition, it
is possible to photograph an abnormally black subject correctly as
a not gray but black subject, so that it is possible to achieve a
correct amount of exposure at all times.
[0220] Incidentally, although the above-described embodiment has
the arrangement in which the camera system automatically detects
focal length information and the like relative to the lens system,
the camera system may be arranged so that the photographer can
input such focal length information or the like through an
operating member such as a button.
[0221] In addition, the present camera system may also be provided
with means for allowing the photographer to input reflectance
information relative to a subject into the camera system, and even
if the amount of emission of the main emission is corrected on the
basis of the input reflectance information, it is possible to
obtain effects similar to the above-described ones.
[0222] Although the above-described embodiment is arranged to
detect whether the flash unit 18 is in the bounce state and correct
the amount of emission of the main emission according to the
detection result, it is also possible to correct the amount of
emission of the main emission in a manner similar to the
above-described one not by detecting not whether the flash unit 18
is in the bounce state but by detecting whether the flash unit 18
is located at a position away from the camera body 1 or whether the
flash unit 18 is a ring flash unit for macrophotography.
[0223] FIGS. 12 to 15 show an embodiment which is arranged to
perform control of the amount of emission of the main emission by
finally measuring film-surface-reflected light. The camera system
shown in FIG. 12 in cross section is substantially identical to
that shown in FIG. 1. Referring to only parts different from those
shown in FIG. 1, reference numeral 23 denotes a light measuring
lens for measuring light on a film surface, and reference numeral
24 denotes a light-on-film-surface measuring sensor. Similarly to
the multiple divided light measuring sensor 7, the
light-on-film-surface measuring sensor 24 is arranged to divide the
image plane into a plurality of areas, perform light measurement
for each of the divided areas, and output measured light
information. The divided areas of the light-on-film-surface
measuring sensor 24 correspond to the divided areas of the multiple
divided light measuring sensor 7.
[0224] FIG. 13 is a circuit block diagram similar to FIG. 3,
showing the circuits of the camera body 1 and the lens barrel 11.
The arrangement of FIG. 13 differs from that of FIG. 3 in that a
light-on-film-surface measuring circuit 114 is provided for
transmitting measured light information received from the
light-on-film-surface measuring sensor 24 to the camera
microcomputer 100.
[0225] The operation flow of this embodiment will be described
below with reference to FIGS. 14 and 15. The circled letter "A" of
the flow of FIG. 14 is connected to the circled letter "A" of the
flow of FIG. 5.
[0226] In Steps S614 to S617, processing computations similar to
Step S114 to S117 are executed. In Step S618, correction of
abnormal reflection is executed, as will be described later in
detail.
[0227] Then, in Step S619, similarly to Step S122, the shutter 8
and the photographing lens diaphragm 15 are controlled to start an
exposure operation. Then, when the switch SWX is turned on in
synchronism with the timing at which the shutter 8 is fully opened
(Step S620), the signal SWX is transmitted to the flash-unit
microcomputer 200 as an instruction to execute the main
emission.
[0228] At the same time that the instruction is transmitted, in
Step S621, the camera microcomputer 100 drives the
light-on-film-surface measuring circuit 114 to cause the
light-on-film-surface measuring sensor 24 to start a light
measuring operation. Then, in Step S622, when the camera
microcomputer 100 determines that the measured light integral value
of the light-on-film-surface measuring circuit 114 has reached a
predetermined value for the light measuring area selected in Step
S622, the camera microcomputer 100 transmits an emission stop
instruction to the flash unit 18 to stop the emission of the flash
unit 18. The predetermined value is a value corrected by the
abnormal-reflection correction of Step S618. In Step S623, one
photographic cycle is brought to an end, similarly to Step
S124.
[0229] The abnormal-reflection correcting routine executed in Step
S618 will be described below with reference to FIG. 15. First, in
Steps S701 to S703, the camera microcomputer 100 performs
processing computations similar to Step S301 to S303.
[0230] Then, in Step S703, the camera microcomputer 100 compares
"level.3", and the preliminary-emission reflected light component
"EVdf(P)" relative to the light measuring area selected for
computing the amount of correct emission of the main emission. If
the preliminary-emission reflected light component "EVdf(P)" is not
greater than "level.3", the process proceeds to Step S704, in which
the camera microcomputer 100 substitutes "0" for the amount of
correction "com_level", and then brings this routine to an end.
[0231] On the other hand, if the preliminary-emission reflected
light component "EVdf(P)" is greater than "level.3", the process
proceeds to Step S705, in which the camera microcomputer 100
corrects the preliminary-emission reflected light component
"EVdf(P)" as follows:
com_level.rarw.EVdf(P)-level.3
[0232] and brings this routine to an end. In this manner, by
controlling the main emission in Step S622 ("correct exposure
level" minus "con level"), the amount of emission of the main
emission is corrected so that the main emission is effected at an
underexposure level.
[0233] According to the embodiment described above, it is possible
to realize a simple camera system capable of providing a correct
amount of exposure at all times without using a complicated
arrangement for special photography, such as bounce flash
photography, even in the case of flash emission control using
film-surface-reflected light measurement.
[0234] The present invention is applicable to not only a camera
system in which a flash unit is separably secured to a camera body,
but also a flash-unit integrated type of camera system.
[0235] The present invention is not applied to only a single-lens
reflex camera, and can also be applied to various types of cameras
such as a lens shutter camera or a video camera, optical
apparatuses other than such cameras, apparatuses other than the
optical apparatuses, apparatuses applied to the cameras or to the
optical or other apparatuses, or elements which constitute part of
such apparatuses.
[0236] The operation of a flash-unit control system according to
another embodiment of the present invention will be described below
with reference to the operation flowchart shown in FIGS. 16 through
21. Incidentally, the following description is mainly focused on
the operation of the camera microcomputer 100 which is associated
with the flowchart shown in FIGS. 16 through 21.
[0237] When the operation of the camera system is started, the
camera microcomputer 100 first clears a flag F_ELK to "0" in Step
S100.
[0238] After that, Steps S101 to S109 are executed. Since Steps
S101 to S109 are identical to the corresponding steps shown in FIG.
5, the description thereof is omitted for the sake of
simplicity.
[0239] In Step S110, the camera microcomputer 100 reads the state
of the preliminary emission lock switch SWFELK which is interlocked
with the aforesaid push switch, and determines whether the
preliminary emission lock switch SWFELK is on or off.
[0240] The process branches from Step S110 to Steps S111 and S113,
and if the preliminary emission lock switch SWFELK is on, the
process proceeds to Step S111, in which control of the preliminary
emission is executed.
[0241] A routine for controlling the preliminary emission control
routine will be described below with reference to FIG. 18.
[0242] In Step S201, the camera microcomputer 100 obtains a subject
luminance immediately before the preliminary emission through the
light measuring circuit 106. The obtained subject luminance value
is memorized in the RAM as Eva (i) (i=0-5).
[0243] In Step S202, the camera microcomputer 100 transmits to the
flash unit 18 an instruction to execute the preliminary emission.
The flash-unit microcomputer 200 performs a preliminary emission
operation in the above-described manner in accordance with the
instruction.
[0244] In Step S203, while the flat emission of the preliminary
emission is being sustained, the camera microcomputer 100 obtains a
subject luminance through the light measuring circuit 106. The
obtained subject luminance value is memorized in the RAM as EVf (i)
(i=0-5).
[0245] Then, the process returns to Step S112 of FIG. 16, in which
the camera microcomputer 100 sets the value of flag F_FELK to 111".
This flag means that the preliminary emission pointed at the
subject intentionally selected by the photographer has been
executed.
[0246] If it is determined in Step S110 that the preliminary
emission lock switch SWFELK is off, the process immediately
proceeds to Step S113, whereas if it is determined in Step S110
that the preliminary emission lock switch SWFELK is on, the process
proceeds to Step S113 through Steps S111 and S112. In Step S113,
the camera microcomputer 100 determines whether the switch SW2 is
on, the switch SW2 being arranged to be turned on when the release
button is pressed to the second stroke position. If the switch SW2
is off, Steps S101 to S110 are repeated, whereas if the switch SW2
is on, the process proceeds to a shutter release operation which
starts with Step S125.
[0247] In Step S125, the camera microcomputer 100 determines
whether the value of the flag F_FELK is "1" or "0". If the value of
the flag F_FELK is "1", this indicates that the preliminary
emission has already been completed. Therefore, the camera
microcomputer 100 proceeds to Step S114 without executing Step
S126.
[0248] If the value of the flag F_FELK is "0", this indicates that
the preliminary emission has not yet been performed. Therefore, the
camera microcomputer 100 proceeds to Step S126, in which
preliminary emission control similar to Step S111 is executed.
[0249] The processing of Steps S114 to S124 is identical to that of
Steps S114 to S124 of FIG. 6, and the description thereof is
omitted for the sake of simplicity. However, since the subject-area
selection routine of Step S117 of FIG. 17 differs from that of Step
S117 of the embodiment shown in FIG. 6, the following description
will be focused on Step S117 of FIG. 17.
[0250] The subject-area selection routine of Step S117 of FIG. 17
will be described below with reference to FIG. 19.
[0251] In Step S301, the camera microcomputer 100 determines
whether the camera system is in the AF mode for performing an
automatic focus detecting operation or the MF mode in which no
automatic focus detecting operation is performed, similarly to Step
S103. If the AF mode has been selected, the process proceeds to
Step S305, whereas if the MF mode has been selected, the process
proceeds to Steps S302.
[0252] In Step S302, the camera microcomputer 100 determines
whether the value of the flag F_FELK is "1" or "0". If the value is
"1", this indicates that the photographer has performed the
preliminary emission prior to an exposure operation. Therefore, the
camera microcomputer 100 proceeds to Step S311 without executing
Steps S303 and S304, and selects a subject area to which to
correctly adjust the amount of emission, without taking account of
the focal length information "f".
[0253] If the value of the flag F_FELK is "0", the process proceeds
to Steps S303 and S304, in which the camera microcomputer 100
selects a subject area while taking account of the focal length
information "f".
[0254] In Step S303, the camera microcomputer 100 obtains the
preliminary-emission reflected light component "EVdf" at a most
distant position beyond which a subject such as a person becomes
excessively small with respect to one light measuring area, from
the focal length information "f", the amount of emission of the
preliminary emission "Qpre" and the predetermined coefficient "c1",
and sets the obtained reflected light component as "level.1".
[0255] In Step S304, the camera microcomputer 100 determines
whether the preliminary-emission reflected light component
"EVdf(Focus.P)" obtained at a light measuring point is not less
than the aforesaid "level.1". If the preliminary-emission reflected
light component "EVdf(Focus.P)" obtained at the light measuring
point is not less than "level.1", the process proceeds to Step
S311. On the other hand, if the preliminary-emission reflected
light component "EVdf(Focus.P)" is less than "level.1", the process
proceeds to Step S305.
[0256] In Step S305, if it is determined in Step S301 that the
camera system is in the MF mode in which no automatic focus
detecting operation is performed, and if it is determined in Step
S304 that the preliminary-emission reflected light component
"EVdf(Focus.P)" is less than "level.1" and the light measuring area
which contains the light measuring point cannot be selected as an
area to which to correctly adjust the amount of emission, the
camera microcomputer 100 selects the area "Close.P" in which a
subject nearest to the camera system is present, from the central
three light measuring areas E0, E1 and E2. This selection method is
based on the concept that there is a highest possibility that a
subject which is nearest to the camera system of all the subjects
present in the image plane is a main subject. Specifically, a light
measuring area in which the preliminary-emission reflected light
component "EVdf(i)" (i=0-2) reaches a maximum is set to the area
"Close.P".
[0257] Then, in Step S306, the camera microcomputer 100 determines
whether the value of the flag F_FELK is "0" or "1". If the value is
"1", this indicates that the photographer has performed the
preliminary emission prior to an exposure operation. Therefore, the
camera microcomputer 100 proceeds to Step S312 without executing
Steps S307 and S308, and selects a subject area to which to
correctly adjust the amount of emission, without taking account of
the focal length information "f".
[0258] If the value of the flag F_FELK is "0", the camera
microcomputer 100 proceeds to Step S307 and S308 and selects a
subject area while taking account of the focal length information
"f".
[0259] In Step S307, the camera microcomputer 100 obtains the
preliminary-emission reflected light component "EVdf" at a most
distant position beyond which a subject such as a person becomes
excessively small with respect to one light measuring area, from
the focal length information "f", the amount of emission of the
preliminary emission "Qpre" and the predetermined coefficient "c2",
and sets the obtained reflected light component as "level.2".
[0260] Although "level.2" is set in a manner identical to that used
for finding "level.1" in Step S303, the value of "level.2" is set
higher than that of "level.1" on the basis of the concept of
weighting a light measuring point to a further extent. For this
reason, even if a subject such as a person lies considerably near
the camera system, the preliminary-emission reflected light
component "EVdf" becomes less than that "level.2". This "level.2"
employs, for example, the value of the preliminary-emission
reflected light component "EVdf" which is obtained when a gray wall
of standard reflectance is present at a position which is
approximately 2.5 mm away from a lens having a focal length of 50
mm.
[0261] Then, in Step S308, the camera microcomputer 100 determines
whether the preliminary-emission reflected light component
"EVdf(Close.P)" obtained at the closest-distance point is not less
than the aforesaid "level.2". If the reflected light component
"EVdf(Close.P)" is not less than "level.2", the process proceeds to
Step S312, whereas if the reflected light component "EVdf(Close.P)"
is less than "level.2", the process proceeds to Step S309.
[0262] If the preliminary-emission reflected light component
"EVdf(Close.P)" obtained at the closest-distance point is less than
"level.2", this indicates that a subject such as a person is
present at a position considerably away from the camera system or
in a peripheral portion of the image plane. Accordingly, in Step
S309, the camera microcomputer 100 selects a subject area to which
to correctly adjust the amount of emission, while taking account of
not only the central three areas E0, E1 and E2 but also the
peripheral areas E3 and E4. Step S309 is shown in FIG. 21, but
since the flow of FIG. 21 is identical to that shown in FIG. 9, the
description thereof is omitted for the sake of simplicity.
[0263] In Step S310, the camera microcomputer 100 selects a light
measuring area having the maximum preliminary-emission reflected
light component from the preliminary-emission reflected light
component "EVdf(Close.P)" relative to the one of the central three
light measuring areas which contains the closest-distance point and
the corrected preliminary-emission reflected light component "EVdf"
relative to the area E3 or E4, which has been calculated in Step
S309, and sets the selected light measuring area as an area to
which to correctly adjust the amount of emission and brings this
routine to an end.
[0264] If it is determined in Step S302 that the value of the flag
F_ELK is "1", this indicates that the photographer has executed the
preliminary emission pointed at a subject to which to correctly
adjust the amount of emission of the flash unit 18 before starting
an exposure operation, with the subject being located in a
particular light measuring area which contains a distance measuring
point on the photographic image plane within the viewfinder 5. If a
decision like Step S304 is made as to such a light measuring area,
the intention of the photographer will be impaired. Accordingly, in
Step S311, the camera microcomputer 100 selects the light measuring
area which contains the distance measuring point, as an area to
which to correctly adjust the amount of emission, and brings this
routine to an end.
[0265] If the preliminary-emission reflected light component
"EVdf(Focus.P)" which is obtained at the light measuring point is
not less than "level.1", this indicates that a subject such as a
person is sufficiently large with respect to the light measuring
area which contains the light measuring point, and that the
preliminary-emission reflected light component "EVdf" has been
accurately measured, irrespective of the value of the flag F_FELK.
Therefore, the light measuring area "Focus.P" which contains the
light measuring point is selected as an area to which to correctly
adjust the amount of emission of the flash unit 18, and the process
brings this routine to an end.
[0266] If it is determined in Step S306 that the value of the flag
F_FELK is "1", this indicates that the photographer has executed
the preliminary emission pointed at a subject to which to correctly
adjust the amount of emission of the flash unit 18 before starting
an exposure operation, with the subject being located in or near
the center of the photographic image plane within the viewfinder 5.
If a decision like Step S308 is made as to a light measuring area
in or near the center which contains a subject present at a
comparatively short distance from the camera system, the intention
of the photographer will be impaired. Accordingly, in Step S312,
the camera microcomputer 100 selects the light measuring area which
contains the closest-distance point (Close.P), as an area to which
to correctly adjust the amount of emission, and brings this routine
to an end.
[0267] If it is determined in Step S308 that the
preliminary-emission reflected light component "EVdf(Focus.P)"
which is obtained at the closest-distance point is not less than
"level.2", this indicates that a subject such as a person is
sufficiently large with respect to the light measuring area which
contains the closest-distance point, and that the
preliminary-emission reflected light component "EVdf" has been
accurately measured, irrespective of the value of the flag F_FELK.
Therefore, the light measuring area "Focus.P" which contains the
closest-distance point is selected as an area to which to correctly
adjust the amount of emission of the flash unit 18, and the process
brings this routine to an end.
[0268] FIG. 20 shows the abnormal-reflection correcting routine of
Step S118 of FIG. 17. The processing of Step S118 of FIG. 17
differs from the processing of Step S118 of FIG. 6, as will be
described below.
[0269] In Step S401, the camera microcomputer 100 determines
whether the value of the flag F_FELK is "0" or "1". If the value is
"1", this indicates that the photographer has performed the
preliminary emission prior to an exposure operation. Therefore, the
camera microcomputer 100 immediately brings this routine to an end
without executing correction of abnormal correction.
[0270] If the value of the flag F_FELK is "0", the process proceeds
to Step S402 to execute correction of abnormal reflection.
[0271] In Step S402, the camera microcomputer 100 obtains the
preliminary-emission reflected light component "EVdf" at a position
at which a subject such as a person is substantially nearest to the
camera system, from the focal length information "f", the amount of
emission of the preliminary emission "Qpre" and the predetermined
coefficient "c3", and sets the obtained reflected light component
as "level.3".
[0272] This "level.3" employs, for example, the value of the
preliminary-emission reflected light component "EVdf" which is
obtained when a gray wall of standard reflectance is present at a
position which is approximately 0.5 mm away from a lens having a
focal length of 50 mm. This is based on the concept that if a lens
having a focal length of 50 mm is used, a subject is not at all
present within the shortest photographing distance (approximately
0.5 m) of the lens.
[0273] In Step S403, the camera microcomputer 100 compares the
aforesaid "level.3" and the preliminary-emission reflected light
component "EVdf(P)" relative to the light measuring area to which
to correctly adjust the amount of emission. If the
preliminary-emission reflected light component "EVdf(P)" is not
greater than "level.3", the camera microcomputer 100 brings this
routine to an end.
[0274] On the other hand, if the preliminary-emission reflected
light component "EVdf(P)" is greater than "level.3", the process
proceeds to Step S404, in which the camera microcomputer 100 sets
the preliminary-emission reflected light component "EVdf(P)" as
follows:
EVdf(P).rarw.level.3
[0275] and brings this routine to an end. By correcting the
preliminary-emission reflected light component "EVdf(P)" in this
manner, the amount of emission of the main emission is corrected so
that the main emission is effected at an underexposure level.
[0276] As described above, according to the present embodiment, the
method of finding a light measuring area to be selected for
correcting the amount of emission of the main emission or for
correctly controlling the amount of emission is altered according
to whether the photographer has intentionally executed the
preliminary emission before an exposure operation, so that it is
possible to realize a flash photography camera system capable of
providing a correct amount of exposure suited to the intention of
the photographer at all times.
[0277] Although the above-described embodiment is arranged so that
the photographer performs the preliminary emission beforehand by
operating a push button, the present invention is not limited to
only such arrangement, and a lever or a dial may be employed. It is
also possible to adopt an arrangement in which the preliminary
emission is performed in interlocked relation to the switch SW1
which is turned on at the first stroke of the release button, by a
setting member.
[0278] The present invention is applicable to not only a camera
system in which a flash unit is separably secured to a camera body,
but also a flash-unit integrated type of camera system.
[0279] The present invention is applicable to not only a
single-lens reflex camera but also other types of cameras such as a
lens shutter camera.
[0280] FIG. 22 is a flowchart of a modification of the
abnormal-reflection correction described above with reference to
FIG. 20.
[0281] In Step S601, the camera microcomputer 100 determines
whether the value of the flag F_FELK is "0" or "1". If the value is
"1", this indicates that the photographer has performed the
preliminary emission prior to an exposure operation. Therefore, the
camera microcomputer 100 immediately brings this routine to an end
without executing correction of abnormal correction.
[0282] If the value of the flag F_ELK is "0", the process proceeds
to Step S602 to execute correction of abnormal reflection.
[0283] In Step S602, the camera microcomputer 100 obtains the
preliminary-emission reflected light component "EVdf" at a position
at which a subject such as a person is substantially nearest to the
camera system, from the subject distance information "Dist_min"
which has been sent from the lens barrel 11 in Step S108, the
amount of emission of the preliminary emission "Qpre" and the
predetermined coefficient "c3.1", and sets the obtained reflected
light component as "level.3.1".
[0284] In Step S603, the camera microcomputer 100 compares the
aforesaid "level.3.1" and the preliminary-emission reflected light
component "EVdf(P)" relative to a selected light measuring area to
which to correctly adjust the amount of emission. If the
preliminary-emission reflected light component "EVdf(P)" is not
greater than "level.3.1", the process proceeds to Step S604. If the
preliminary-emission reflected light component "EVdf(P)" is greater
than "level.3.1", the process proceeds to Step S607.
[0285] In Step S604, the camera microcomputer 100 obtains the
preliminary-emission reflected light component "EVdf" at a position
at which a subject such as a person is most distant from the camera
system, from the maximum subject distance information "Dist_max"
which has been sent from the lens barrel 11 in Step S108, the
amount of emission of the preliminary emission "Qpre" and the
predetermined coefficient "c3.2", and sets the obtained reflected
light component as "level.3.2".
[0286] In Step S605, the camera microcomputer 100 compares the
aforesaid "level.3.2", and the preliminary-emission reflected light
component "EVdf(P)" relative to the selected light measuring area
to which to correctly adjust the amount of emission. If the
preliminary-emission reflected light component "EVdf(P)" is less
than "level.3.2", the process proceeds to Step S606. If the
preliminary-emission reflected light component "EVdf(P)" is not
less than "level.3.2", the camera microcomputer 100 determines that
the distance range of the maximum subject distance information
"Dist_max", which has been sent from the lens barrel 11, and the
value of the preliminary-emission reflected light component
"EVdf(P)" correctly agree with each other and there is no
abnormality. Then, the camera microcomputer 100 brings this routine
to an end without executing correction of abnormal reflection.
[0287] If the preliminary-emission reflected light component
"EVdf(P)" is less than "level.3.2", in Step S606, the camera
microcomputer 100 sets the preliminary-emission reflected light
component "Evdf(P)" as follows:
EVdf(P).rarw.level.3.2
[0288] and brings this routine to an end. By correcting the
preliminary-emission reflected light component "EVdf(P)" in this
manner, the amount of emission of the main emission is corrected so
that the main emission is effected at an underexposure level.
[0289] If it is determined in Step S603 that the
preliminary-emission reflected light component "EVdf(P)" is greater
than "level.3.1", the process proceeds to Step S607, n which the
camera microcomputer 100 sets the preliminary-emission reflected
light component "EVdf(P)" as follows:
EVdf(P).rarw.level.3.1
[0290] and brings this routine to an end. By correcting the
preliminary-emission reflected light component "EVdf(P)" in this
manner, the amount of emission of the main emission is corrected so
that the main emission is effected at an underexposure level.
[0291] As described above, according to the routine shown in FIG.
22, it is possible to realize a flash photography camera system in
which although the amount of emission is corrected by using the
maximum and minimum values of the distance from the lens barrel 11
to a subject, it is possible to provide a correct amount of
exposure suited to the intention of the photographer at all times,
by altering the status of such correction according to whether the
photographer has intentionally executed the preliminary emission
before an exposure operation.
[0292] FIGS. 23 and 24 are flowcharts showing the routine of
controlling the amount of emission control by means of
film-surface-reflected light measurement in the camera system shown
in FIGS. 12 and 13.
[0293] Since the flowchart of FIG. 23 is substantially identical to
that of FIG. 14 except for Step S720 of FIG. 23, the description of
the entire flowchart is omitted for the sake of simplicity and only
the routine of Step S720 (shown in FIG. 24) will be described
below.
[0294] Since Steps S801 to S803 shown in FIG. 24 are substantially
identical to Steps S401 to S403 of FIG. 20, the description thereof
is omitted for the sake of simplicity.
[0295] In Step S803, the camera microcomputer 100 compares the
aforesaid "level.3" and the preliminary-emission reflected light
component "EVdf(P)" relative to a selected light measuring area to
which to correctly adjust the amount of emission. If the
preliminary-emission reflected light component "EVdf(P)" is not
greater than "level.3", the process proceeds to Step S804, in which
the camera microcomputer 100 substitutes "0" for the amount of
correction "com_level", and then brings this routine to an end.
[0296] On the other hand, if the preliminary-emission reflected
light component "EVdf(P)" is greater than "level.3", the process
proceeds to Step S805, in which the camera microcomputer 100
corrects the preliminary-emission reflected light component
"EVdf(P)" as follows:
com_level.rarw.EVdf(P)-level.3
[0297] and brings this routine to an end. In this manner, the
amount of correction of the amount of emission of the main emission
is obtained and the main emission is controlled in Step S822
("correct exposure level" minus "com_level"), to correct the amount
of emission of the main emission so that the main emission is
effected at an underexposure level.
[0298] FIG. 25 is a diagrammatic cross-sectional view of the
optical arrangement of a camera system, showing another embodiment
of the present invention. In FIG. 25, identical reference numerals
are used to denote constituent elements identical to the
corresponding elements shown in FIG. 12. FIG. 26 is a block diagram
of the electrical circuit of the camera system of FIG. 25, and in
FIG. 26, identical reference numerals are used to denote
constituent elements identical to the corresponding elements of the
camera body and the lens side shown in FIG. 12.
[0299] Referring to FIG. 26, a flash control circuit 115 is
composed of a circuit for enabling communications between the flash
control sensor 24 of a camera and the flash unit 18, and when the
flash unit 18 starts an emission, the flash control sensor
immediately starts to store electric charge. When the output of the
flash control sensor reaches a predetermine value, the flash
control circuit 115 transmits an emission stop signal to the flash
unit 18.
[0300] A flash-unit microcomputer 300 is a circuit which causes the
flash unit 18 to emit light toward a subject, in accordance with a
signal from the camera microcomputer 100, and is capable of
performing various kinds of control, such as control of the amount
of emission and control of the peak value and the emission time of
a flat emission.
[0301] A DC/DC converter 301 boosts a battery voltage in accordance
with an instruction given by the flash-unit microcomputer 300,
thereby charging the main capacitor C1 with a voltage of
approximately 300 V.
[0302] The voltage dividing resistors R1 and R2 are provided so
that the flash-unit microcomputer 300 can monitor the voltage of
the main capacitor C1. The flash-unit microcomputer 300 performs
A/D conversion of a divided voltage supplied from the resistors R1
and R2, through an A/D converter 302, and indirectly monitors the
voltage of the main capacitor C1 to stop the boosting operation of
the DC/DC converter 301, or monitors the current charged voltage of
the main capacitor C1 and transmits the monitored charged voltage
to the camera microcomputer 100.
[0303] A trigger circuit 303 outputs a trigger signal via the
flash-unit microcomputer 300 in response to an instruction of the
camera microcomputer 100 during an exposure operation, and causes
the xenon tube 19 to generate a high voltage. Thus, the charge
energy stored in the main capacitor C1 is discharged via the xenon
tube 19 so that an emission of the flash unit 18 is started.
[0304] An emission stopping circuit 304 is turned on when the
aforesaid trigger signal is outputted. When the emission of the
flash unit 18 is started and the output of the flash control
circuit 115 reaches a predetermined valued, the emission stopping
circuit 304 transmits an emission stop signal to the flash-unit
microcomputer 300, and the flash-unit microcomputer 300 transmits
an emission stop signal to the emission stopping circuit 304. When
receiving the emission stop signal, the emission stopping circuit
304 is turned off to stop the emission of the xenon tube 19.
[0305] The operation flow of the flash photography camera system to
which the present invention is applied will be described below with
reference to FIG. 27.
[0306] When the operation of the camera system is started, the
camera microcomputer 100 detects the state of the first-stroke
switch SW1 which is turned on when the shutter release button is
pressed to the first stroke position (Step Sol). The camera
microcomputer 100 repeats Step S01 until the on state of the
first-stroke switch SW is detected, and if the on state of the
first-stroke switch SW1 is detected, the camera microcomputer 100
performs the next operation.
[0307] In Step S02, the camera microcomputer 100 reads the states
of individual operating switches (not shown) of the camera system
through the switch sense circuit 110, and sets various
photographing modes, such as a method of determining a shutter
speed and a method of determining an aperture value.
[0308] Then, in Step S03, the camera microcomputer 100 causes the
focus detecting circuit 105 to perform a focus detecting operation
using a known phase-difference detecting method, as described
previously. The camera microcomputer 100 controls the lens
microcomputer 112 on the basis of the state of focus detected in
the aforesaid focus detecting operation, and performs focus
adjustment of the lens barrel 11.
[0309] As described previously with reference to FIG. 2, three
points for focus detection are provided on the image plane. Which
of the three points at which subjects are respectively present is
to be focused may be arbitrarily set by the photographer, or by
using a known automatic selection algorithm based on the concept of
nearest-point priority.
[0310] In Step S04, the camera microcomputer 100 obtains the
subject luminance values of the respective six areas provided in
the image plane, through the light measuring circuit 106.
[0311] Then, in Step S05, the camera microcomputer 100 determines
the amount of exposure from the subject luminance values of the
respective six areas by a known algorithm, and determines the value
of a shutter speed and the value of an aperture in accordance with
the photographing modes which have been set.
[0312] Then, in Step S06, the camera microcomputer 100 determines
whether the second-stroke switch SW2 to be turned on when the
shutter release button is pressed to the second stroke position is
on. If the second-stroke switch SW2 is off, the process returns to
Step S01 and repeats the operation of Steps S01 to S06, whereas if
the second-stroke switch SW2 is on, the process proceeds to Step
S07.
[0313] In Step S07, the camera microcomputer 100 obtains the
subject luminance information through the light measuring circuit
106 and calculates the degree of backlighting. A method of finding
the degree of backlighting will be described below with reference
to FIG. 32.
[0314] First, a backlighting coefficient "rlt" is obtained from the
output values of the respective sensor's light measuring areas. The
backlighting coefficient "rlt" is a function which indicates how
the degree of backlighting of the measured light value obtained at
the distance measuring point determined in step S03 is higher than
the degree of backlighting of an average measured light value. As
the value of the backlighting coefficient "rlt" becomes smaller,
the contrast of a subject becomes higher and the degree of
backlighting becomes higher. The backlighting coefficient "rlt" is
expressed by the following expression: 1 rt1 = j = 0 5 A ( j ) / 6
- A ( i )
[0315] where A(i) represents the measured light value of the
distance measuring point, and A(0) to A(5) represent the measured
light outputs obtained from the respective six light measuring
areas E0 to E5 shown in FIG. 2.
[0316] The degree of backlighting, rV, which is calculated on the
basis of this backlighting coefficient is expressed by the
following expression, and the relationship between the backlighting
coefficient "rlt" and the degree of backlighting "rV" is as shown
in FIG. 32: 2 rV = { 1.5 ( rlt > 2 ) rlt ( rdt rlt 2 ) 0 ( rlt
< rdt )
[0317] The units of the backlighting coefficient and the degree of
backlighting are equivalent to those of the APEX system.
[0318] In Step S08, the camera microcomputer 100 computes a
correction value of the amount of emission from the degree of
backlighting obtained in Step S07. A method of finding the
correction value of the amount of emission will be described below
with reference to FIG. 33.
[0319] The amount of correction, .DELTA.G, of the amount of
emission varies depending on the degree of backlighting and the
luminance and is expressed by the following expression: 3 G = { 0 (
A AV BV7 ) rV .times. CBV .times. ( A AV - DG ) ( A AV > BV7
)
[0320] where A.sub.AV is a simple average value of measured light
values. In other words, as the degree of backlighting becomes
higher under higher-luminance conditions, the amount of correction
.DELTA.G becomes larger.
[0321] In Step S09, the camera microcomputer 100 moves up the main
mirror 2 and retracts the main mirror 2 from the photographic
optical path together with the sub-mirror 25, prior to an exposure
operation.
[0322] Then, in Step S10, the camera microcomputer 100 gives the
lens microcomputer 112 an instruction to find an aperture value
based on the determined exposure value, and drives the shutter
control circuit 107 so that the shutter 8 can be controlled to run
at the determined shutter speed.
[0323] In Step S11, the flash-unit microcomputer 300 is caused to
control the main emission of the flash unit 18 during the exposure
operation in synchronism with the driving of the shutter 8. The
main emission is controlled by a known TTL flash control system,
and is restricted to the amount of emission corrected by the amount
of correction obtained by the computation of Step S08. The
relationship between the amount of correction and a correct value
is expressed by the following expression:
G=C-.DELTA.G
[0324] where G is the sensor output (integral value) obtained from
the flash control sensor when the flash control sensor sends an
emission stop signal to the flash unit 18, and C is a theoretical
correct value obtainable in TTL flash control.
[0325] When the exposure operation comes to an end in this manner,
in Step S12, the camera microcomputer 100 moves down the main
mirror 2 and the like which have been retracted from the
photographing optical path, thereby again obliquely inserting the
main mirror 2 and the like into the photographing optical path. The
camera microcomputer 100 winds the film 9 by one frame by means of
the motor control circuit 108 and the film running detecting
circuit 109, and the operation of the flash photography camera
system according to the aforesaid embodiment is completed.
[0326] FIG. 28 is a diagrammatic cross-sectional view mainly
showing an optical arrangement according to another embodiment of
the present invention. In FIG. 28, identical reference numerals are
used to denote constituent elements identical to the corresponding
ones shown in FIGS. 12 and 25, and the description thereof is
omitted for the sake of simplicity.
[0327] Referring to FIG. 28, a glass fiber 30 is provided for
conducting light emitted from the xenon tube 19 to the monitor
sensor (PD1) 31. The sensor (PD1) 31 is provided for directly
measuring the amounts of emissions of the preliminary emission and
the main emission. The sensor (PD2) 32 is provided for monitoring
the light emitted from the xenon tube 19. By controlling the
emission current of the xenon tube 19 on the basis of the output of
the sensor (PD2) 32, the flash unit 18 can be made to perform a
flat emission.
[0328] FIG. 29 is a block diagram showing the electrical circuit of
the camera system of FIG. 28.
[0329] In FIG. 29, identical reference numerals are used to denote
constituent elements identical to the corresponding elements shown
in FIG. 26, and the description thereof is omitted for the sake of
simplicity.
[0330] Referring to FIG. 29, the trigger circuit 303 outputs a
trigger signal via the flash-unit microcomputer 300 in response to
an instruction of the camera microcomputer 100 during an exposure
operation, and causes the xenon tube 19 to generate a high voltage.
Thus, the charge energy stored in the main capacitor C1 is
discharged via the xenon tube 19 so that an emission of the flash
unit 18 is started.
[0331] The emission stopping circuit 304 is turned on when the
aforesaid trigger signal is outputted. After the emission of the
flash unit 18 has been started, the emission stopping circuit 304
is turned off to stop the emission of the xenon tube 19, in
response to the output of a comparator 305 or a comparator 306 and
a signal from the flash-unit microcomputer 300.
[0332] The electrical circuit shown in FIG. 29 will be described
below together with individual operations of the flash unit 18.
Preliminary Flat Emission (FP Emission)
[0333] The flash-unit microcomputer 300 sets a predetermined value
in a D/A converter 307. At this time, since the xenon tube 19 has
not yet started to emit light, a substantial amount of
photoelectric current does not flow in the monitor sensor (PD2) 32
and a second monitor circuit 309 outputs a small-level signal to
the inverting input terminal of the comparator 306, so that the
comparator 306 outputs a high-level signal to the emission stopping
circuit 304.
[0334] When a trigger signal is outputted, the xenon tube 19 starts
an emission and the peak value of the emission immediately rises
and the photoelectric current of the sensor (PD2) 32 increases, and
the output of the second monitor circuit 309 rises and the output
of the comparator 306 goes to its low level.
[0335] When the output of the comparator 306 goes to the low level,
the emission stopping circuit 304 is activated to shut down the
discharge loop of the xenon tube 19, but since a circulating
current loop is formed by the diode DD1 and the coil L1, the peak
value falls not instantaneously but gradually.
[0336] As the peak value falls, the photoelectric current of the
sensor (PD2) 32 decreases, so that the output of the comparator 306
goes to the high level, and the discharge loop of the xenon tube 19
is formed and the peak value again starts to rise.
[0337] In this manner, the increase and the decrease in the peak
value are repeated at intervals of a period shorter than the period
required for the output of the comparator 306 to change between the
low level and the high level, so that it is possible to realize
control of the flat emission of continuing an emission while
maintaining an approximately constant peak value.
[0338] The flat emission is brought to an end when the flash-unit
microcomputer 300 outputs a signal directly to the emission
stopping circuit 304.
[0339] The peak value of the flat emission can be controlled to
become a desired value, by varying the operating point of the
photoelectric current of the sensor (PD2) 32 by changing the
digital value of the predetermined value to be applied to the D/A
converter 307 and changing the level of a voltage to be applied to
the non-inverting input terminal of the comparator 306. Similarly,
the emission time of the flat emission can also be controlled to
become a desired value.
Preliminary Emission and Integration
[0340] The preliminary emission is realized by performing the
above-described flat emission for a predetermined time with a
predetermined peak value.
[0341] During the preliminary emission, the monitor sensor (PD1) 31
measures the luminance of the light emitted from the xenon tube 19,
and when the flash-unit microcomputer 300 instructs an integrating
circuit 311 to start an integration, the integrating circuit 311
starts to integrate the preliminary emission in response to the
output of a first monitor circuit 310. Incidentally, although the
output of the comparator 305 to the inverting input terminal of
which the output of the integrating circuit 311 is applied is
inputted to the emission stopping circuit 304, the emission
stopping circuit 304 is set to ignore such input, by a signal from
the flash-unit microcomputer 300, so that the control of the
above-described flat emission is prevented from being hindered.
[0342] When the preliminary emission of predetermined time comes to
an end, the flash-unit microcomputer 300 causes the A/D converter
302 to perform A/D conversion of the preliminary emission integral
value outputted from the integrating circuit 311 and reads the
integral value as a digital value.
Main Emission Control
[0343] The camera microcomputer 100 obtains a correct integral
value of the amount of emission of the main emission from a value
such as the aforementioned preliminary emission integral value or a
subject-reflected light luminance value supplied from the multiple
divided light measuring sensor 7 during the preliminary emission,
and sets the obtained correct integral value in the D/A converter
307 via the flash-unit microcomputer 300.
[0344] The camera microcomputer 100 initializes the integrating
circuit 311 and causes the trigger circuit 303 to start an emission
of the xenon tube 19.
[0345] The emission luminance of the xenon tube 19 which has been
measured by the monitor sensor (PD1) 31 is integrated by the
integrating circuit 311, and when the integral output of the
integrating circuit 311 reaches the set correct integral value, the
output of the comparator 305 is switched from high to low and the
emission stopping circuit 304 stops the emission. Incidentally,
during this time, the emission stopping circuit 304 is set to
ignore the output of the comparator 306, by a signal supplied from
the flash-unit microcomputer 300.
[0346] In this manner, the amount of emission of the main emission
can be controlled to become the correct amount of emission obtained
by the computation.
[0347] The operation of the camera system according to the
above-described embodiment will be described below with reference
to FIGS. 30 and 31. FIG. 30 is a flowchart aiding in mainly
describing the operation of the camera microcomputer (MPU) 100,
while FIG. 31 is a flowchart aiding in describing processing which
constitutes the essential feature of the embodiment, and shows
expressions associated with the processing.
[0348] In the flowchart shown in FIG. 30, when the operation of the
camera system is started, the camera microcomputer (MPU) 100
detects the state of the first-stroke switch SW1 which is turned on
when the shutter release button is pressed to the first stroke
position (Step S01). The camera microcomputer (MPU) 100 repeats
Step S01 until the on state of the first-stroke switch SW1 is
detected, and if the on state of the first-stroke switch SW1 is
detected, the camera microcomputer (MPU) 100 performs the next
operation.
[0349] In Step S02, the camera microcomputer (MPU) 100 reads the
states of individual operating switches (not shown) of the camera
system through the switch sense circuit 110, and sets various
photographing modes, such as a method of determining a shutter
speed and a method of determining an aperture value.
[0350] Then, in Step S03, the camera microcomputer (MPU) 100 causes
the focus detecting circuit 105 to perform a focus detecting
operation using a known phase-difference detecting method, as
described previously. The camera microcomputer (MPU) 100 controls
the lens microcomputer 112 on the basis of the state of focus
detected in the aforesaid focus detecting operation, and performs
focus adjustment.
[0351] As described previously with reference to FIG. 2, three
points for focus detection are provided on the image plane. Which
of the three points at which subjects are respectively present is
to be focused may be arbitrarily set by the photographer, or by
using a known automatic selection algorithm based on the concept of
nearest-point priority.
[0352] In Step S04, the camera microcomputer (MPU) 100 obtains the
subject luminance values of the respective six areas provided in
the image plane, through the light measuring circuit 106.
[0353] Then, in Step S05, the camera microcomputer (MPU) 100
determines the amount of exposure from the subject luminance values
of the respective six areas by a known algorithm, and determines
the value of a shutter speed and the value of an aperture in
accordance with the photographing modes which have been set.
[0354] Then, in Step S06, the camera microcomputer (MPU) 100
determines whether the second-stroke switch SW2 to be turned on
when the shutter release button is pressed to the second stroke
position is on. If the second-stroke switch SW2 is off, the process
returns to Step S01 and repeats the operation of Steps S01 to S06,
whereas if the second-stroke switch SW2 is on, the process proceeds
to Step S07.
[0355] In Step S07, the camera microcomputer (MPU) 100 obtains
information indicative of the current charged voltage of the main
capacitor C1 of the flash unit 18 through information transmission
from the flash-unit microcomputer 300. The camera microcomputer
(MPU) 100 also obtains information indicative of the absolute
distance from the camera system to a subject through information
transmission from the lens microcomputer 112, and obtains subject
luminance information from the light measuring circuit 106.
[0356] In Step S08, the camera microcomputer (MPU) 100 determines
the amount of emission of the preliminary emission on the basis of
the obtained charged voltage information, absolute distance
information and subject luminance information.
[0357] In Step S09, the camera microcomputer (MPU) 100 sends an
instruction to the flash-unit microcomputer 300 so that the
flash-unit microcomputer 300 controls the preliminary emission to
make the amount of emission thereof equivalent to the determined
amount of emission.
[0358] In Step S10, simultaneously with the preliminary emission,
the camera microcomputer (MPU) 100 measures the light reflected
from the subject, through the multiple divided light measuring
sensor 7. More specifically, the camera microcomputer (MPU) 100
also measures the luminance of the subject through the multiple
divided light measuring sensor 7 immediately before the start of
emission of the preliminary emission. This measurement is intended
to obtain a measured value of subject-reflected light which
contains only the emission component of the preliminary emission,
by subtracting the measured light value obtained immediately before
the preliminary emission from the measured light value obtained
during the preliminary emission.
[0359] While the preliminary emission is being performed, the
flash-unit microcomputer 300 causes the monitor sensor (PD1) 31 to
measure the direct light of the xenon tube 19, and then causes the
integrating circuit 311 to integrate the measured light value
supplied from the monitor sensor (PD1) 31. Upon completion of the
preliminary emission, the flash-unit microcomputer 300 performs A/D
conversion of the integral value of the integrating circuit 311 and
obtains the digital integral value.
[0360] In Step S11, the camera microcomputer (MPU) 100 computes a
correct integral value of the main emission from the measured light
integral value of the preliminary emission, the measured light
value of the subject-reflected light of the preliminary emission,
the exposure value and the like.
[0361] In Step S12, the camera microcomputer (MPU) 100 obtains the
subject luminance information from the light measuring circuit 106
and calculates the degree of backlighting which indicates how a
main subject contrasts with a background.
[0362] In Step S13, the camera microcomputer (MPU) 100 computes the
amount of correction of the amount of emission from the degree of
backlighting obtained in Step S12.
[0363] In Step S14, the camera microcomputer (MPU) 100 moves up the
main mirror 2 and retracts the main mirror 2 from the photographic
optical path together with the sub-mirror 25, prior to an exposure
operation.
[0364] Then, in Step S15, the camera microcomputer (MPU) 100 gives
the lens microcomputer 112 an instruction to find an aperture value
based on the determined amount of exposure, and drives the shutter
control circuit 107 so that the shutter 8 can be controlled to run
at the determined shutter speed.
[0365] In Step S16, the flash-unit microcomputer 300 is caused to
control the main emission during the exposure operation in
synchronism with the driving of the shutter 8. The main emission is
controlled on the basis of the sum of the amount of correction
obtained by the computation of Step S11 and the amount of
correction obtained by the computation of Step S13.
[0366] When the exposure operation comes to an end in this manner,
in Step S17, the camera microcomputer (MPU) 100 moves down the main
mirror 2 and the like which have been retracted from the
photographing optical path, thereby again obliquely inserting the
main mirror 2 and the like into the photographing optical path. The
camera microcomputer (MPU) 100 winds the film 9 by one frame by
means of the motor control circuit 108 and the film running
detecting circuit 109, and the operation of the flash photography
camera system according to the aforesaid embodiment is
completed.
[0367] The following description is made in connection with
computing expressions for computing the amount of correct emission
of the main emission and the amount of emission of the preliminary
emission in the camera system according to the above-describe
embodiment, as well as a flowchart of FIG. 31.
[0368] In Step S001 which corresponds to Step S04 of the flowchart
of FIG. 30, the camera microcomputer (MPU) 100 measures the subject
luminance values of the respective six areas under natural light
through the light measuring circuit 106 and obtains a weighted
average of the six subject luminance values: 4 EVb = L N 2 i = - 5
W ( i ) .times. 2 EVb ( i ) i = 0 5 W ( i )
[0369] where the weighting coefficient W(i) varies according to the
kind of light measuring mode used in main-emission control and the
states of distance measuring points selected for automatic focus
detection. The weighting coefficient W(i) is set as shown in Table
2 by way of example.
2 TABLE 2 w(i) WEIGHTED LIGHT PARTIAL LIGHT MEASURMENT MEASUREMENT
DISTANCE i P0 P1 P2 P0 P1 P2 .rarw. MEASURING 0 7 3 1 1 0 0 POINT 1
3 7 3 0 1 0 2 1 3 7 0 0 1 3 3 1 1 0 0 0 4 1 1 3 0 0 0 5 1 1 1 0 0
0
[0370] According to Table 2, if the light measuring mode used in
the main-emission control is the weighted average light measurement
mode, a weighted average of the luminance values obtained at the
respective distance measuring points selected for automatic focus
detection is computed. If the light measuring mode used in the
main-emission control is the partial light measurement mode, a
weighted average is computed in such a way that a luminance value
relative to only an area which contains a selected distance
measuring point is multiplied by the weighting coefficient and
luminance values relative to the other areas are reset to "0", the
subject luminance value EVb(i) relative to one area is obtained as
EVb.
[0371] In the computation of the weighted average, the
logarithmically compressed values EVb(i) of the luminance values
relative to the respective areas are raised to the second power and
expanded into antilogarithms, and a weighted average of the
antilogarithms is calculated. The weighted average is finally
logarithmically compressed with base 2.
[0372] The value EVb obtained by this computation is used in a
main-emission correct ratio computation to be performed in Step
S009 in the flowchart shown in FIG. 31 which will be described
later.
[0373] In Step S002 which corresponds to Step S02 of the flowchart
of FIG. 30, the photographer or the like intentionally inputs a
photographing mode, such as a shutter speed priority mode or an
aperture value priority mode, various control values and other
associated data. In Step S003, an exposure value "EVs" consisting
of a shutter speed "TV" and an aperture value "AV" is determined
from the input photographing mode, the control values and EVb(i) of
the subject luminances.
EVs=TV+AV
[0374] To determine this exposure value, the weighted average EVb
obtained in Step S001 may be used, or a known divided measurement
computation algorithm may also be used.
[0375] In Step S004 which corresponds to Step S10 of the flowchart
of FIG. 30, subject luminances are measured immediately before the
preliminary emission and a weighted average of the measured subject
luminances is calculated. 5 EVa = L N 2 i = - 5 W ( i ) .times. 2
EVa ( i ) i = 0 5 W ( i )
[0376] The computing method is the same as Step S001. The reason
why light measurement and a computation similar to those of Step
S001 are performed will be described below.
[0377] There is a possibility that the photographer may change
framing and the state of a subject may change at an intermediate
time instant between the instant when the first-stroke switch SW1
is turned on and the instant when the second-stroke switch SW2 is
turned on immediately before the start of an exposure operation.
The succeeding preliminary emission and hence light measurement for
the preliminary emission needs to be performed for a short time in
order to prevent a waste of energy and to prevent a subject to be
photographed from being dazzled by the preliminary emission.
Accordingly, in the light measurement of Step S001, light
measurement of comparatively long time is repeated and the obtained
measured light values are averaged in order to reduce the influence
of flicker as greatly as possible during photography under a light
source, such as a fluorescent lamp, as shown in FIG. 34. However,
the light measurement of Step S004 needs to be performed for a
short time which is equal to the time required for light
measurement to be performed during the succeeding preliminary
emission, and at the possible shortest time interval between the
light measurement of Step S004 and the light measurement of the
preliminary emission.
[0378] The computed value Eva is used in the main-emission correct
ratio computation (Step S009) which will be described later, in
order to compute subject-reflected light which contains only the
reflected-light component of the preliminary emission.
[0379] Then, control of the preliminary emission is performed in
Steps S007 which corresponds to Step S09 of FIG. 30. The amount of
emission of the preliminary emission is determined in the sequence
of Steps S005 and S006.
[0380] In Step S005 which corresponds to Step S07 of FIG. 30, a
main-capacitor charged voltage vc, subject luminance information
EVb and subject distance information Dist are inputted, and in Step
S006 which corresponds to Step S08 of FIG. 30, the amount of
emission of the preliminary emission "Q" is computed.
Q=k.times.F.sub.1(Vc).times.F.sub.2(EVb).times.F.sub.3(Dist)
[0381] The functions F.sub.1, F.sub.2 and F.sub.3 will be described
below with reference to FIGS. 35(a) to 35(c).
[0382] FIG. 35(a) is a graph of the function F.sub.1. As the
main-capacitor charged voltage Vc becomes higher, the amount of
emission of the preliminary emission "Q" is made larger. Although
the larger the amount of emission of the preliminary emission "Q",
the wider the dynamic range of light measurement of
subject-reflected light, the function F.sub.1 is intended to
prevent the energy of the main emission from being consumed by the
preliminary emission when the main-capacitor charged voltage Vc is
low.
[0383] FIG. 35(b) is a graph of the function F.sub.2. Since the
subject-reflected light component of the preliminary emission might
be concealed by a high subject luminance under natural light, the
amount of emission of the preliminary emission needs to be made
large. Contrarily, if the preliminary emission is carried out when
the subject luminance is high under natural light, a subject to be
photographed may be dazzled by a sudden emission. Accordingly, the
amount of emission of the preliminary emission needs to be reduced.
When the subject luminance is high or low to some extent, the
amount of emission of the preliminary emission is kept constant,
because the amount of emission of the preliminary emission is
difficult to increase or decrease by hardware.
[0384] FIG. 35(c) is a graph of the function F.sub.3. If the
absolute distance from the camera to a subject to be photographed
is close, since the subject is dazzled by the preliminary emission,
the amount of emission of the preliminary emission needs to be
reduced. Contrarily, if the absolute distance is far, since the
preliminary emission does not reach a subject to be photographed
and subject-reflected light cannot be measured, the amount of
emission of the preliminary emission needs to be increased. When
the absolute distance is far or close to some extent, the amount of
emission of the preliminary emission is kept constant similarly to
the case of the function F.sub.2.
[0385] Specifically, the increase and the decrease in the amount of
emission of the preliminary emission are controlled by a rise and a
fall in the peak value of the flat emission.
[0386] In Step S008 which corresponds to Step S10 of the flowchart
of FIG. 30, the subject-reflected light luminances of the
preliminary emission are measured, and a weighted average of the
measured luminances is obtained. 6 EVf = L N 2 i = - 5 W ( i )
.times. 2 EVf ( i ) i = 0 5 W ( i )
[0387] The timing is as shown in FIG. 34, and the weighted average
is computed in a manner similar to used in Steps S001 and S004.
[0388] In Step S009 which corresponds to Step S11 of the flowchart
of FIG. 30, the amount of correct emission of the main emission
relative to the amount of emission of the preliminary emission is
computed.
r1=LN.sub.2(2.sup.EVs-2.sup.EVb)-LN.sub.2(2.sup.EVf-2.sup.EVa)
(A)
r2=EV.sub.S-1.5-LN.sub.2(2.sup.EVf2.sup.EVa)+rV (B)
[0389] In the first term of Expression (A), the exposure value
"EVs" and the measured subject luminance value "EVb" are raised to
the second power and expanded into antilogarithms, and the
difference between the antilogarithms is calculated and is
logarithmically compressed with base 2. In this computation, the
amount of underexposure for subject luminance under natural light
is computed. Specifically, the total amount of exposure of the
subject is made correct in such a way as to obtain the amount of
correct exposure by adding subject luminance under an emission of
the flash unit 18 to subject luminance under natural light.
[0390] In the second term of Expression (A), similarly, the
subject-reflected light luminance "EVf" obtained during the
preliminary emission and the subject luminance "EVa" obtained
immediately before the preliminary emission are raised to the
second power and expanded into antilogarithms, and the difference
between the antilogarithms is calculated, and is logarithmically
compressed with base 2. This computation obtains the
subject-reflected light luminance of only the preliminary emission,
exclusive of the subject luminance under natural light.
[0391] The first term of Expression (B) represents that the value
of the first term of the Expression (A) is not greater than "0",
i.e., the exposure value "EVs" is less than the measured subject
luminance value "EVb", i.e., a correct exposure can be obtained
without the use of the flash unit 18. In this case, a desired
emission level is set to the amount of emission equivalent to a
1.5-step underexposure level relative to a control value. The
amount of emission equivalent to the 1.5-step underexposure level
has been determined on the basis of the data obtained by actually
taking pictures. The content of the second term of Expression (B)
is identical to the content of the second term of Expression
(A).
[0392] The third term of Expression (B) represents backlight
correction, and the backlighting coefficient "rlt" shown in FIG. 32
is used as a parameter. If backlight is strong, correction is
performed so that the amount of correction is increased toward an
overexposure side. The amount of correction in backlight correction
has been determined on the basis of the data obtained by actually
taking pictures.
[0393] In either of Expressions (A) or (B), by subtracting the
value of the second term from that of the first term, because of
their compression computations, it is possible to obtain a ratio
which indicates to what extent the amount of emission of the main
emission is to be increased or decreased with respect to the amount
of emission of the preliminary emission so that the total amount of
exposure can be made correct.
[0394] After that, the larger value of the two values of r1 and r2
is selected as a control value. Although the larger value is
selected as a control value, if EVs>EVf, the value of r1 is
used, and if EVs.ltoreq.EVf, the value of r2 is used.
[0395] Basically, if the subject luminance is greater than the
control value, the value of r2 is used, whereas if the subject
luminance is less than the control value, the value of r1 is used.
However, in the case of backlight conditions, the control value
varies depending on the correction value of the third term of
Expression (B).
[0396] In Step S010 which corresponds to Step S10 of the flowchart
of FIG. 30, an integral value of the measured light value of the
direct light of the xenon tube 19 during the preliminary emission
is set as a variable "pre_int". In Step S011 which corresponds to
Step S11 of the flowchart of FIG. 30, a correct integral value of
the main emission is computed:
main_int=pre_int+r+TV-t_pre+c
[0397] where all the variables are compression variables.
[0398] The xenon tube 19 may be made to perform a flat emission
while the shutter 8 is open, on the basis of a peak value
equivalent to the value obtained by adding the ratio "r" obtained
in Step S009 to the peak value of the preliminary emission. Since
such peak value is converted into an integral value, a time factor
of "the shutter time (TV)--the preliminary emission continuation
time (t-pre)" may further be added to the peak value of the
preliminary emission. FIG. 34 shows the manner of the computation
performed in Step S011.
[0399] A method of finding the degree of backlighting will be
described below with reference to FIG. 32.
[0400] First, the backlighting coefficient "rlt" is obtained from
the output values of the respective sensor's light measuring areas.
The backlighting coefficient "rlt" is a function which indicates
how the degree of backlighting of the measured light value obtained
at the distance measuring point determined in Step S03 is higher
than the degree of backlighting of an average measured light value
(an average value of the measured light values of the areas E0 to
E5). As the value of the backlighting coefficient "rlt" becomes
smaller, the contrast of a subject becomes higher and the degree of
backlighting becomes higher. The backlighting coefficient "rlt" is
expressed by the following expression: 7 rt1 = j = 0 5 A ( j ) / 6
- A ( i )
[0401] where A(i) represents the measured light value of the
distance measuring point determined in Step S03, and A(0) to A(5)
represent the measured light outputs obtained from the respective
six light measuring areas E0 to E5 shown in FIG. 2.
[0402] The degree of backlighting, rV, which is calculated on the
basis of this backlighting coefficient is expressed by the
following expression, and the relationship between the backlighting
coefficient "rlt" and the degree of backlighting "rV" is as shown
in FIG. 32: 8 rV = { 1.5 ( r1t > 2 ) r1t ( rdt r1t 2 ) 0 ( r1t
< rdt )
[0403] The units of the backlighting coefficient and the degree of
backlighting are equivalent to those of the APEX system.
[0404] A method of finding the correction value of the amount of
emission will be described below with reference to FIG. 33.
[0405] The amount of correction, .DELTA.G, of the amount of
emission varies depending on the degree of backlighting and the
luminance and is expressed by the following expression: 9 G = { 0 (
A AV BV7 ) rV .times. CBV .times. ( A AV - DG ) ( A AV > BV7
)
[0406] where A.sub.AV is a simple average value of measured light
values. In other words, as the degree of backlighting becomes
higher under higher-luminance conditions, the amount of correction
.DELTA.G becomes larger.
[0407] Finally, a correction coefficient, such as the amount of
correction for flash control, which is set by the photographer, is
added.
[0408] In Step S014 which corresponds to Step S14 of the flowchart
of FIG. 30, the amount of emission of the main emission is
controlled on the basis of the correct integral value of the main
emission obtained through the computation.
[0409] FIG. 36 is a block diagram showing another embodiment of the
present invention. The optical arrangement of a camera system
according to this embodiment is identical to that shown in FIG. 28.
In FIG. 36, identical reference numbers are used to denote
constituent elements identical to the corresponding ones shown in
FIG. 29. In FIG. 36, reference numeral 110' denotes a dial switch
circuit for indicating the state of a dial switch, shown in FIG.
37, which corresponds to any of the setting positions of the dial
switch. The switch sense circuit 110 reads the setting position of
the dial switch through the dial switch circuit 110'.
[0410] The shown dial switch is used to selectively set the
photographing modes. If the shown dial switch is set so that a
position "L" is opposed to the mark shown as a triangle in FIG. 37,
a lock mode for turning off the power supply of the camera system
is set. Similarly, a position "p" is provided for setting a program
mode in which the camera system determines a shutter speed and an
aperture value according to a subject luminance, a position "Tv" is
provided for setting a shutter speed priority AE mode in which the
camera system determines an aperture value according to a subject
luminance when a photographer himself/herself determines a shutter
speed, a position "Av" is provided for setting an aperture priority
AE mode in which the camera system determines a shutter speed
according to a subject luminance when a photographer
himself/herself determines an aperture value, a position "M" is
provided for setting a manual mode in which a photographer
himself/herself determines a shutter speed and an aperture value, a
position "DEP" is provided for setting a depth-of-field priority AE
mode in which when a photographer inputs a positional range to be
focused, the camera system automatically sets an aperture value and
a shutter speed.
[0411] In addition, a position "CF" is provided for setting a
custom function setting mode, and a position "CAL" is provided for
setting a visual line calibration mode.
[0412] The image select zone shown in FIG. 37 is provided for
setting an image select mode in which the camera system performs
exposure control so that even a beginner can easily enjoy
photography. A full automatic mode, a portrait mode, a landscape
mode, a close-up mode and a sports mode can be selectively set by
the photographer rotating the dial switch from the "L" side, so
that the photographer can take a photograph suited to a desired
scene.
[0413] The operation of the camera microcomputer (MPU) 100 will be
described below with reference to FIG. 38.
[0414] When the operation of the camera system is started, the
process proceeds to Step S01, in which the camera microcomputer
(MPU) 100 determines whether the switch SW1 is on. If the switch
SW1 is off, the camera microcomputer (MPU) 100 repeats Step S01,
and if the switch SW1 is on, the process proceeds to Step S02.
[0415] In Step S02, the camera microcomputer (MPU) 100 reads the
states of the dial switch and other operating switches (not shown)
of the camera system other than the switches SW1 and SW2, through
the switch sense circuit 110, and sets various photographing modes,
such as a method of determining a shutter speed and a method of
determining an aperture value.
[0416] In Step S03, the camera microcomputer (MPU) 100 drives the
focus detecting circuit 105 to perform a focus detecting operation
using a known phase-difference detecting method in the manner
described previously. The camera microcomputer (MPU) 100 also
controls the lens microcomputer 112 to perform focus adjustment, on
the basis of the state of focus detected in the focus detecting
operation.
[0417] Three points for focus detection are provided on the image
plane, as described previously with reference to FIG. 2. Which of
the three points at which subjects are respectively present is to
be focused may be arbitrarily determined by the photographer, or
may be determined by executing a known automatic selection
algorithm based on the concept of nearest-point priority.
[0418] In Step S04, the camera microcomputer (MPU) 100 obtains the
subject luminance values of the respective six areas provided in
the image plane, through the light measuring circuit 106.
[0419] In Step S05, the camera microcomputer (MPU) 100 determines
the amount of exposure from the subject luminance values of the
respective six areas by a known algorithm, and determines the value
of a shutter speed and the value of an aperture in accordance with
the photographing modes which have been set. During the program
mode using the flash unit 18, the camera microcomputer (MPU) 100
sets a shutter speed and an aperture value according to a subject
luminance on the basis of the program diagram shown in FIG. 40.
This program diagram is dedicated to a 50-mm lens having a
fully-open-aperture F number of 1.8, and if the subject luminance
is high when the full automatic mode of the image select (IS) mode
is selected, the highest shutter speed is limited to {fraction
(1/125)} sec, as shown by a dashed line in FIG. 40.
[0420] In Step S06, the camera microcomputer (MPU) 100 determines
whether the image select mode is selected. The image select mode
includes light measuring modes which are symbolically displayed on
the dial switch by using icons, as shown in FIG. 37. If the image
select mode is selected, the camera system can set an optimum
program diagram so that even a beginner can easily take a
comparatively beautiful picture. If it is determined that the image
select mode is selected, the process proceeds to Step S07, whereas
if the image select mode is not selected, the process proceeds to
Step S08.
[0421] In Step S07, since the image select mode has been selected,
the value of an FP emission enable Flag FP_ON provided in the
camera microcomputer (MPU) 100 is reset to "0" to inhibit an FP
emission. FIG. 41 is a table showing the contents of the FP
emission enable Flag FP_ON. The value of the FP emission enable
Flag FP_ON is set to "1" at all times, and even if the value of the
FP emission enable Flag FP ON is "0", the value is set to "1" upon
completion of photography.
[0422] Then, in Step S08, the camera microcomputer (MPU) 100
determines whether the switch SW2 is on. If the switch SW2 is off,
the process returns to Step S01 and repeats Steps S01 to S08. If
the switch SW2 is on, the process proceeds to Step S09.
[0423] In Step S09, the camera microcomputer (MPU) 100 obtains
information indicative of the current charged voltage of the main
capacitor C1 of the flash unit 18 through information transmission
from the flash-unit microcomputer 300. The camera microcomputer
(MPU) 100 also obtains information indicative of the absolute
distance from the camera system to a subject through information
transmission from the lens microcomputer 112, and obtains subject
luminance information from the light measuring circuit 106.
[0424] In Step S10, the camera microcomputer (MPU) 100 determines
the amount of emission of the preliminary emission on the basis of
the obtained charged voltage information, absolute distance
information and subject luminance information.
[0425] In Step S11, the camera microcomputer (MPU) 100 sends an
instruction to the flash-unit microcomputer 300 so that the
flash-unit microcomputer 300 controls the preliminary emission of
the flat emission to make the amount of emission of the preliminary
emission equivalent to the determined amount of emission.
[0426] In Step S12, simultaneously with the preliminary emission,
the camera microcomputer (MPU) 100 measures the light reflected
from the subject, through the multiple divided light measuring
sensor 7. More specifically, the camera microcomputer (MPU) 100
also measures the luminance of the subject through the multiple
divided light measuring sensor 7 immediately before the start of
emission of the preliminary emission. This measurement is intended
to obtain a measured value of subject-reflected light which
contains only the emission component of the preliminary emission,
by subtracting the measured light value obtained immediately before
the preliminary emission from the measured light value obtained
during the preliminary emission.
[0427] While the preliminary emission is being performed, the
flash-unit microcomputer 300 causes the monitor sensor (PD1) 31 to
measure the direct light of the xenon tube 19, and then causes the
integrating circuit 311 to integrate the measured light value
supplied from the monitor sensor (PD1) 31. Upon completion of the
preliminary emission, the flash-unit microcomputer 300 performs A/D
conversion of the integral value of the integrating circuit 311 and
obtains the digital integral value.
[0428] In Step S13, the camera microcomputer (MPU) 100 computes a
correct integral value of the main emission from the measured light
integral value of the preliminary emission, the measured light
value of the subject-reflected light of the preliminary emission,
the exposure value and the like. The processing of Step S13 is the
same as that described previously in connection with each of the
aforesaid embodiments.
[0429] In Step S14, the camera microcomputer (MPU) 100 moves up the
main mirror 2 and retracts the main mirror 2 from the photographic
optical path together with the sub-mirror 25, prior to an exposure
operation.
[0430] Then, in Step S15, the camera microcomputer (MPU) 100 gives
the lens microcomputer 112 an instruction to find an aperture value
based on the determined amount of exposure, and drives the shutter
control circuit 107 so that the shutter 8 can be controlled to run
at the determined shutter speed.
[0431] In Step S16, the flash-unit microcomputer 300 is caused to
control the main emission during the exposure operation in
synchronism with the driving of the shutter 8. The main emission is
controlled to become a main flat emission based on the amount of
correction obtained by the computation of Step S13. This control is
identical to that described previously in connection with each of
the aforesaid embodiments, and the description thereof is omitted
for the sake of simplicity.
[0432] If the FP emission enable Flag FP_ON is "0", the main flat
emission is inhibited in Step S07 and a normal emission is
performed in Step S16. Accordingly, it is possible to prevent
occurrence of an underexposure even if the distance to a main
subject is long or a larger aperture value is selected, so that
even a photographer such as a beginner who selects the image select
mode can perform photography without failure. Incidentally, the
normal emission is controlled so that its amount of emission
becomes equivalent to the amount of emission determined according
to the computed value obtained in Step S13 and the amount of
emission of the preliminary flat emission obtained in Step S12.
[0433] When the exposure operation comes to an end in this manner,
in Step S17, the camera microcomputer (MPU) 100 moves down the main
mirror 2 and the like which have been retracted from the
photographing optical path, thereby again obliquely inserting the
main mirror 2 and the like into the photographing optical path. The
camera microcomputer (MPU) 100 winds the film 9 by one frame by
means of the motor control circuit 108 and the film running
detecting circuit 109, and the operation of the camera system is
completed.
[0434] FIG. 39 shows an operation flow of the camera microcomputer
(MPU) 100 of another embodiment of the flash photography camera
system according to the present invention. Although in the
flowchart of FIG. 38 the main flat emission is inhibited when the
image select mode is set, the flowchart of FIG. 39 is characterized
in that even when the image select mode is set, the main flat
emission is enabled if predetermined conditions are satisfied.
[0435] In the flowchart of FIG. 39, when the operation of the
camera system is started, the process proceeds to Step S101, in
which the camera microcomputer (MPU) 100 determines whether the
switch SW1 is on. If the switch SW1 is off, the camera
microcomputer (MPU) 100 repeats Step S101, and if the switch SW1 is
on, the process proceeds to Step S102.
[0436] In Step S102, the camera microcomputer (MPU) 100 reads the
states of the dial switch and other operating switches (not shown)
of the camera system other than the switches SW1 and SW2, through
the switch sense circuit 110, and sets various photographing modes,
such as a method of determining a shutter speed and a method of
determining an aperture value.
[0437] In Step S103, the camera microcomputer (MPU) 100 drives the
focus detecting circuit 105 to perform a focus detecting operation
using a known phase-difference detecting method in the manner
described previously. The camera microcomputer (MPU) 100 also
controls the lens microcomputer 112 to perform focus adjustment, on
the basis of the state of focus detected in the focus detecting
operation.
[0438] Three points for focus detection are provided on the image
plane, as described previously with reference to FIG. 2. Which of
the three points at which subjects are respectively present is to
be focused may be arbitrarily determined by the photographer, or
may be determined by executing a known automatic selection
algorithm based on the concept of nearest-point priority.
[0439] In Step S104, the camera microcomputer (MPU) 100 obtains the
subject luminance values of the respective six areas provided in
the image plane, through the light measuring circuit 106.
[0440] In Step S105, the camera microcomputer (MPU) 100 determines
the amount of exposure from the subject luminance values of the
respective six areas by a known algorithm, and determines the value
of a shutter speed and the value of an aperture in accordance with
the photographing modes which have been set. During the program
mode using the flash unit 18, the camera microcomputer (MPU) 100
sets a shutter speed and an aperture value according to a subject
luminance on the basis of the program diagram shown in FIG. 40.
This program diagram is dedicated to a 50-mm lens having a
fully-open-aperture F number of 1.8, and if the subject luminance
is high when the full automatic mode of the image select (IS) mode
is selected, the highest shutter speed is limited to {fraction
(1/125)} sec, as shown by a dashed line in FIG. 40.
[0441] In Step S106, the camera microcomputer (MPU) 100 determines
whether the image select mode is selected. If the image select mode
is selected, the process proceeds to Step S107, whereas if the
image select mode is not selected, the process proceeds to Step
S110.
[0442] In Step S107, the camera microcomputer (MPU) 100 determines
whether the portrait mode or the close-up mode of the image select
mode is selected. If neither of the portrait mode and the close-up
mode is selected, the process proceeds to Step S109 in order to
inhibit an FP emission. If either of the portrait mode and the
close-up mode is selected, the process proceeds to Step S108.
[0443] In Step S108, the camera microcomputer (MPU) 100 determines
whether the measured light value is greater than a predetermined
value EVi. This EVi is expressed by the following expression:
EVi=(maximum aperture value of lens)+(flash-synchronizing shutter
speed of camera)-(film sensitivity)
[0444] In this expression, each value is computed on the basis of
the APEX system. For example, if a photographing lens system has a
maximum aperture value of F22 and a camera body has a
flash-synchronizing shutter speed of {fraction (1/125)} second and
a film having a film sensitivity of ISO 100 is used, the value of
EVi is EVi=9+7-5=11. If the measured light value (in this example,
a Bv value) is greater than this value, it is determined that an FP
emission is possible, and the process proceeds to Step S110. If the
measured light value is not greater than the value of EVi, the
process proceeds to Step S109.
[0445] In Step S109, if the image select mode has been selected,
the value of the FP emission enable Flag FP_ON provided in the
camera microcomputer (MPU) 100 is reset to "0" to inhibit the FP
emission.
[0446] In Step S110, the value of the FP emission enable Flag FP_ON
is set to "1", and the process proceeds to Step S111.
[0447] Then, in Step S111, the camera microcomputer (MPU) 100
determines whether the switch SW2 is on. If the switch SW2 is off,
the process returns to Step S101 and repeats Steps S101 to S110. If
the switch SW2 is on, the process proceeds to Step S112.
[0448] Steps S112 to S120 are identical to Steps S9 to S17 of FIG.
38, and the description thereof is omitted for the sake of
simplicity.
[0449] If it is determined in the aforesaid step S108 that the
measured light value is not greater than the predetermined value
EVi, the main flat emission is inhibited (Step S119) and a normal
emission is performed, so that occurrence of an underexposure is
prevented. On the other hand, if it is determined in Step S108 that
the measured light value is greater than the predetermined value
EVi, the main flat emission is enabled so that flash photography is
performed to prevent occurrence of an overexposure.
[0450] FIG. 42 is a block diagram showing another embodiment of the
present invention. The optical arrangement of a camera system
according to this embodiment is identical to that shown in FIG. 1.
In FIG. 42, identical reference numbers are used to denote
constituent elements identical to the corresponding ones shown in
FIG. 29. In FIG. 42, reference numeral 33 denotes a switch for
detecting the direction of an emission part during the execution of
a bounce function, and symbol FELK denotes a switch to be turned on
in response to an operation of an operating member (not shown).
[0451] The operation of the camera microcomputer (MPU) 100 of this
embodiment will be described below with reference to FIGS. 43(a)
and 43(b).
[0452] Referring first to FIG. 43(a), when the operation of the
camera system is started, the process proceeds to Step S01, in
which the camera microcomputer (MPU) 100 initializes predetermined
input/output ports and variables. In Step S02, the camera
microcomputer (MPU) 100 reads lens information, such as focus
information and full-open-aperture F number, from the lens barrel
11. In Step S03, the camera microcomputer (MPU) 100 reads
flash-unit information, such as the guide number and the state of
the flash unit 18, from the flash unit 18.
[0453] Then, in Step S04, the camera microcomputer (MPU) 100
determines whether the direction of the flash unit 18 has been
changed by the execution of the bounce function, on the basis of
the output of the switch 33 which is contained in the flash-unit
information. If the direction of the flash unit 18 has been
changed, the process proceeds to Step S05, in which the flag FELK
(FE lock) is cleared to zero, whereas if the direction of the flash
unit 18 has not been changed, the process proceeds to Step S06.
[0454] In Step S06, the camera microcomputer (MPU) 100 reads the
states of the dial switch and other operating switches (not shown)
of the camera system other than the switches SW1 and SW2, through
the switch sense circuit 110, and sets various photographing modes,
such as a method of determining a shutter speed and a method of
determining an aperture value.
[0455] In Step S06', the camera microcomputer (MPU) 100 determines
whether an aperture stopping-down switch (not shown) has been
manually operated when the camera system is in the manual mode or
in the aperture-priority mode. If the aperture stopping-down switch
has been manually operated to cause the camera system to come into
an aperture stopping-down mode, the process proceeds to step S06",
in which the aperture size of the diaphragm 15 is reduced to an
arbitrary aperture value which has previously been set in the
manual mode or the aperture-priority mode.
[0456] In Step S07, the camera microcomputer (MPU) 100 determines
whether the switch SW1 to be turned on at the first stroke of the
shutter release button is on. If the switch SW1 is off, the process
proceeds to Step S08, in which the camera microcomputer (MPU) 100
determines whether a light measuring timer (a timer for counting
time so that light measurement can be continued for approximately 6
seconds after the switch SW1 is turned off) is performing its
counting operation. If the light measuring timer is performing the
counting operation, the process proceeds to Step S12, whereas if
the light measuring timer completes the counting operation, the
process proceeds to Step S09.
[0457] In Step S09, the camera microcomputer (MPU) 100 determines
whether the switch SW1 has just been turned off. If the switch SW1
has not just been turned off, the process proceeds to Step S11, in
which the flag FELK is cleared, and the flowchart is brought to an
end. On the other hand, if the switch SW1 has just been turned off,
the process proceeds to Step S10, in which the light measuring
timer is made to start the counting operation, and the process
proceeds to Step S12.
[0458] In Step S12, the camera microcomputer (MPU) 100 obtains the
subject luminance values of the respective six areas provided in
the image plane, through the light measuring circuit 106.
[0459] In Step S13, the camera microcomputer (MPU) 100 determines
the amount of exposure from the subject luminance values of the
respective six areas by a known algorithm, and determines the value
of a shutter speed and the value of an aperture in accordance with
the photographing modes which have been set.
[0460] In Step S14, the camera microcomputer (MPU) 100 determines
whether the flag FELK is on. If the flag FELK is off, the process
proceeds to Step S18, whereas if the flag FELK is on, the process
proceeds to Step S15.
[0461] In Step S15, the camera microcomputer (MPU) 100 executes a
preliminary emission and performs light measurement. The content of
this processing will be described later.
[0462] In Step S16, the flag FELK is set to "1".
[0463] In Step S17, the camera microcomputer (MPU) 100 determines
whether the switch SW2 to be turned on at the second stroke of the
shutter release button is on. If the switch SW2 is off, the process
proceeds to Step S18, in which the camera microcomputer (MPU) 100
drives the focus detecting circuit 105 to perform a focus detecting
operation using a known phase-difference detecting method in the
manner described previously. The camera microcomputer (MPU) 100
also controls the lens microcomputer 112 to perform focus
adjustment, on the basis of the state of focus detected in the
focus detecting operation.
[0464] Three points for focus detection are provided on the image
plane, as described previously with reference to FIG. 2. Which of
the three points at which subjects are respectively present is to
be focused may be arbitrarily determined by the photographer, or
may be determined by executing a known automatic selection
algorithm based on the concept of nearest-point priority.
[0465] The process returns from Step S18 to Step S02, and as long
as the switch SW1 is on or the light measuring timer is performing
the counting operation, the camera microcomputer (MPU) 100 repeats
Step S02 to Step S18.
[0466] If it is determined in Step S17 that the switch SW2 is on,
the process proceeds to Step S19.
[0467] In Step S19, the camera microcomputer (MPU) 100 executes a
preliminary emission and performs light measurement. The
preliminary-emission and light-measurement processing subroutine
executed in Step S19 is identical to that executed in Step S15.
[0468] In Step S5 of the preliminary-emission and light-measurement
processing subroutine shown in FIG. 43(b), it is determined whether
the flag FELK is set. If the flag FELK is set, this subroutine is
brought to an end, whereas if the flag FELK is not set, the process
proceeds to Step S26, in which the processing of fully opening the
aperture of the diaphragm 15 is executed, because the diaphragm of
the lens system may be stopped down as a result of the execution of
a function such as a depth-of-field confirmation function. By fully
opening the aperture prior to the preliminary emission in this
manner, it is possible to perform a later preliminary emission
light measurement through accurate and simple computations.
[0469] In Step S27, the camera microcomputer (MPU) 100 obtains
information indicative of the current charged voltage of the main
capacitor C1 of the flash unit 18 through information transmission
from the flash-unit microcomputer 300. The camera microcomputer
(MPU) 100 also obtains information indicative of the absolute
distance from the camera system to a subject through information
transmission from the lens microcomputer 112, and obtains subject
luminance information from the light measuring circuit 106.
[0470] In Step S28, the camera microcomputer (MPU) 100 determines
the amount of emission of the preliminary emission on the basis of
the obtained charged voltage information, absolute distance
information and subject luminance information.
[0471] In Step S29, the camera microcomputer (MPU) 100 sends an
instruction to the flash-unit microcomputer 300 so that the
flash-unit microcomputer 300 controls the preliminary emission of
the flat emission to make the amount of emission of the preliminary
emission equivalent to the determined amount of emission.
[0472] In Step S30, simultaneously with the preliminary emission,
the camera microcomputer (MPU) 100 measures the light reflected
from the subject, through the multiple divided light measuring
sensor 7. More specifically, the camera microcomputer (MPU) 100
also measures the luminance of the subject through the multiple
divided light measuring sensor 7 immediately before the start of
emission of the preliminary emission, and obtains a measured value
of subject-reflected light which contains only the emission
component of the preliminary emission, by subtracting the measured
light value obtained immediately before the preliminary emission
from the measured light value obtained during the preliminary
emission.
[0473] While the preliminary emission is being performed, the
flash-unit microcomputer 300 causes the monitor sensor (PD1) 31 to
measure the direct light of the xenon tube 19, and then causes the
integrating circuit 311 to integrate the measured light value
supplied from the monitor sensor (PD1) 31. Upon completion of the
preliminary emission, the flash-unit microcomputer 300 performs A/D
conversion of the integral value of the integrating circuit 311 and
obtains the digital integral value. Then, the camera microcomputer
(MPU) 100 brings this subroutine to an end.
[0474] In Step S20 which belongs to the main flowchart shown in
FIG. 43(a), the camera microcomputer (MPU) 100 computes a correct
integral value of the main emission from the measured light
integral value of the preliminary emission, the measured light
value of the subject-reflected light of the preliminary emission,
the exposure value and the like.
[0475] In Step S21, the camera microcomputer (MPU) 100 moves up the
main mirror 2 and retracts the main mirror 2 from the photographic
optical path together with the sub-mirror 25, prior to an exposure
operation.
[0476] Then, in Step S22, the camera microcomputer (MPU) 100 gives
the lens microcomputer 112 an instruction to find an aperture value
based on the determined amount of exposure, and drives the shutter
control circuit 107 so that the shutter 8 can be controlled to run
at the determined shutter speed.
[0477] In Step S23, the flash-unit microcomputer 300 is caused to
control the main emission of the flash unit 18 during the exposure
operation in synchronism with the driving of the shutter 8. The
main emission is restricted to the amount of emission obtained by
the computation of Step S20.
[0478] When the exposure operation comes to an end in this manner,
in Step S24, the camera microcomputer (MPU) 100 moves down the main
mirror 2 and the like which have been retracted from the
photographing optical path, and obliquely inserts the main mirror 2
and the like into the photographing optical path, and
simultaneously executes the processing of fully opening the
aperture of the diaphragm 15. The camera microcomputer (MPU) 100
winds the film 9 by one frame by means of the motor control circuit
108 and the film running detecting circuit 109, and returns to Step
S02.
[0479] Incidentally, in this embodiment, if the flag FELK is not be
operated, the aperture of the diaphragm 15 is fully opened and the
preliminary emission and light measurement are performed
immediately before the exposure operation, and after the amount of
emission of the main emission (correct integral value) has been
determined, the main emission and the exposure operation are
performed. At this time, if the switch SW2 remains on, a continuous
shooting is selected and the preliminary emission is performed
immediately before each exposure cycle. The emission operation of
performing the preliminary emission immediately before each
exposure cycle is hereinafter referred to as the "batch emission
mode".
[0480] If the flag FELK is turned on by operating an operating
member (not shown), the aperture of the diaphragm 15 is fully
opened independently of an exposure operation (i.e., before the
operation of the shutter release button) and the preliminary
emission and light measurement are performed to determine the
amount of emission of the main emission (correct integral value).
After that, if the switch SW2 is turned on, the main emission and
the exposure operation are performed on the basis of the determined
amount of emission. At this time, if the switch SW2 remains on, a
continuous shooting is selected, but only the main emission is
performed without performing the preliminary emission immediately
before each exposure cycle, and all the amounts of emissions during
the continuous shooting are controlled to become equal (i.e., to
make the amount of emission of each of the second main emission et
seqq. equal to the amount of emission of the first main emission).
Incidentally, the operation of performing continuous shooting by
using the measured light value of the first preliminary emission as
a fixed value is hereinafter referred to as the "FE lock mode".
[0481] In addition, in this embodiment, as can be seen from Steps
S04 and S05, if the direction of the flash unit 18 is changed by
the execution of the bounce function after the flag FELK has been
operated, the FE lock mode is cancelled the batch emission mode is
set.
[0482] Incidentally, the timing of changing the FE lock mode to the
batch emission mode is not limited to only when the direction of
the flash unit 18 is changed, and the processing of changing the FE
lock mode to the batch emission mode may be performed at the time
of occurrence of a change in a photographic condition which affects
exposure, such as an exchange of photographing lens systems or a
change of photographing modes.
[0483] The following description is made in connection with
computing expressions for computing the amount of correct emission
of the main emission in the above-described camera system, as well
as a flowchart of FIG. 44.
[0484] In Step S001 which corresponds to Step S12 of the flowchart
of FIG. 43(a), the camera microcomputer (MPU) 100 measures the
subject luminance values of the respective six areas under natural
light through the light measuring circuit 106 and obtains a
weighted average of the six subject luminance values. The weighting
coefficient W(i) varies according to the kind of light measuring
mode used in the control of the main emission of the flash unit 18
and the states of distance measuring points selected for automatic
focus detection. The weighting coefficient W(i) is set as listed in
the table shown in FIG. 45 by way of example. As can be seen from
the table, if the light measuring mode used in the main-emission
control is the weighted average light measurement mode, a weighted
average of the luminance values obtained at the respective distance
measuring points selected for automatic focus detection is
computed. If the light measuring mode used in the main-emission
control is the partial light measurement mode, a weighted average
is computed in such a way that a luminance value relative to only
an area which contains a selected distance measuring point is
multiplied by the weighting coefficient and luminance values
relative to the other areas are reset to "0", i.e., the subject
luminance value EVb(i) relative to one area is obtained as EVb.
[0485] In the computation of the weighted average, the
logarithmically compressed values EVb(i) of the luminance values
relative to the respective light measuring areas are raised to the
second power and expanded into antilogarithms, and a weighted
average of the antilogarithms is calculated. The weighted average
is finally logarithmically compressed with base 2.
[0486] The value EVb obtained by this computation is used in a
main-emission correct ratio computation to be performed in Step
S009 which will be described later.
[0487] In Step S002 which corresponds to Step S06 of the flowchart
of FIG. 43(a), the photographer or the like intentionally inputs a
photographing mode, such as a shutter speed priority mode or an
aperture value priority mode, various control values and other
associated data.
[0488] In Step S003, the exposure value "EVs" consisting of the
shutter speed "TV" and the aperture value "AV" is determined from
the input photographing mode, the control values and the subject
luminance values EVb(i), by using the following expression (1):
EVs=TV+AV (1)
[0489] To determine the exposure value EVs, the weighted average
EVb obtained in Step S001 may be used, or a known divided
measurement computation algorithm may also be used.
[0490] In Step S004 which corresponds to Step S30 of the flowchart
of FIG. 43(b), subject luminances are measured immediately before
the preliminary emission and a weighted average of the measured
subject luminances is calculated by using a computing expression
similar to that shown in Step S001 of FIG. 44.
[0491] The reason why light measurement is again performed in Step
S004 after the light measurement of Step S001 is that there is a
possibility that the photographer may change framing or the like
and the state of a subject may change at an intermediate time
instant between the instant when the switch SW1 is turned on and
the instant when the switch SW2 is turned on immediately before the
start of an exposure operation.
[0492] However, in Step S004, the succeeding preliminary emission
and hence light measurement for the preliminary emission needs to
be performed for a short time in order to prevent a waste of energy
and to prevent a subject to be photographed from being dazzled by
the preliminary emission. Accordingly, in the light measurement of
Step S001, light measurement of comparatively long time (for
example, 10 ms) is repeated in order to reduce the influence of
flicker as greatly as possible during photography under a light
source, such as a fluorescent lamp, as shown in FIG. 34. However,
the light measurement of Step S004 needs to be performed for a
short time (for example, 1 ms or less) which is equal to the time
required for light measurement to be performed during the
succeeding preliminary emission (S008),
[0493] Incidentally, it is desirable to perform the light
measurement of Step S004 and the light measurement of Step S008
temporally close to each other so that the light measurement
conditions of both steps can be made as identical to each other as
possible, except whether the flash unit 18 is made to emit
light.
[0494] The computed value EVa is used in the main-emission correct
ratio computation to be performed in Step S009 which will be
described later.
[0495] Then, control of the preliminary emission is performed in
Step S007 which corresponds to Step S29 of the flowchart of FIG.
43(b). The amount of emission of the preliminary emission is
determined in the sequence of Steps S005 and S006 which
respectively correspond to Steps S27 and S29 of the flowchart of
FIG. 43(b).
[0496] In Step S005, the main-capacitor charged voltage Vc, the
subject luminance information EVb and the subject distance
information Dist of the main capacitor C1 are inputted, and in Step
S006, the amount of emission of the preliminary emission "Q" is
computed by using the following expression (2).
Q=k.times.F.sub.1(Vc).times.F.sub.2EVb).times.F.sub.3(Dist) (2)
[0497] As shown in FIG. 35(a), the value of the function F.sub.1
(Vc) is approximately proportional to the main-capacitor charged
voltage Vc. Therefore, if the charged voltage Vc is high, the
amount of emission of the preliminary emission "Q" is increased to
widen the dynamic range of light measurement, whereas if the
charged voltage Vc is low, the amount of emission of the
preliminary emission "Q" is decreased to prevent a shortage of the
energy of the main emission.
[0498] As shown in FIG. 35(b), the value of the function F.sub.2
(EVb) is approximately proportional to the subject luminance EVb
except when the subject luminance EVb is low or high to some
extent. Therefore, if the subject luminance EVb is high under
natural light, the amount of emission of the preliminary emission
"Q" is made large, so that the subject-reflected light component of
the preliminary emission is prevented from being concealed by a
high subject luminance under natural light. Contrarily, if the
subject luminance EVb is low, the amount of emission of the
preliminary emission "Q" is made small, so that a subject to be
photographed is prevented from being dazzled by the preliminary
emission. When the subject luminance EVb is high or low to some
extent, the value of the second function F.sub.2 (EVb) is kept
constant, because the amount of emission of the preliminary
emission is difficult to increase or decrease by hardware.
[0499] As shown in FIG. 35(c), the value of the function F.sub.3
(Dist) is approximately proportional to the subject distance Dist
except when the subject distance Dist is close or far to some
extent. Therefore, if the subject distance Dist is far, the amount
of emission of the preliminary emission "Q" is made large, so that
it is possible to prevent the problem that the light of the
preliminary emission does not reach a subject and subject-reflected
light cannot be obtained. Contrarily, if the subject distance Dist
is close, the amount of emission of the preliminary emission "Q" is
made small, so that a person who is a subject is prevented from
being dazzled by the preliminary emission. When the subject
distance Dist is close or far to some extent, the value of the
third function F.sub.3 (Dist) is kept constant for a reason similar
to that mentioned above in the description of the second function
F.sub.2.
[0500] In Step S008 which corresponds to Step S30 of the flowchart
of FIG. 43(b), the subject-reflected light luminances of the
preliminary emission are measured at the timing shown in FIG. 34,
and a weighted average of the measured luminances is obtained by
the computing expression used in Steps S001 and S004.
[0501] In Step S009, the amount of correct emission of the main
emission relative to the amount of emission of the preliminary
emission is computed by using the following expression (3):
r1=LN.sub.2(2.sup.EVs-2.sup.EVb)-LN.sub.2(2.sup.Evf-2.sup.EVa)
(3)
[0502] In the first term of Expression (3), the exposure value
"EVs" and the measured subject luminance value "EVb" are raised to
the second power and expanded into antilogarithms, and the
difference between the antilogarithms is calculated and is
logarithmically compressed with base 2. In this computation, the
amount of underexposure for subject luminance under natural light
is computed. Specifically, the computation of the first term is
performed in such a way as to obtain a correct amount of exposure
by adding subject luminance under an emission of the flash unit 18
to subject luminance under natural light. In the second term of
Expression (3), the exposure value "EVf" obtained during the
preliminary emission and the measured subject luminance value "EVa"
obtained immediately before the preliminary emission are raised to
the second power and expanded into antilogarithms and the
difference between the antilogarithms is calculated, and is
logarithmically compressed with base 2. This computation can obtain
the subject-reflected light luminance of only the preliminary
emission, exclusive of the subject luminance under natural
light.
[0503] By subtracting the value of the second term from that of the
first term, it is possible to obtain the ratio "r" which indicates
to what extent the amount of emission of the main emission is to be
increased or decreased with respect to the amount of emission of
the preliminary emission so that the total amount of exposure can
be made correct.
[0504] In Step S010 which corresponds to Step S30 of the flowchart
of FIG. 43(b), the integral value "pre.sub.13 int" of the measured
light value of the direct light of the xenon tube 19 during the
preliminary emission is computed.
[0505] In Step S011, the correct integral value "main_mint" of the
main emission is computed by using the following expression
(4):
main_int=pre_int+r+TV-t_pre+c (4)
[0506] where all the variables are logarithmically compressed
numbers. As can be seen from Expression (4) and FIG. 34, the amount
of emission of the main emission (flash emission) is set to be
equal to the value which is obtained by adding the correction
coefficient "c", such as the amount of correction for flash
control, which has been set by the photographer to the amount of
emission to be reached when a flat emission is performed during the
open time (TV) of the shutter 8 at an emission intensity equivalent
to the sum of the emission intensity (pre_int-t_pre) of the
preliminary emission and the ratio "r" obtained in Step S009
(actually, an emission intensity of "r" times that of the
preliminary emission).
[0507] In Step S012 which corresponds to Step S23 of the flowchart
of FIG. 43(a), the amount of emission of the main emission is
controlled on the basis of the correct integral value obtained in
Step S011.
[0508] As described above, in the camera system according to the
above-described embodiment, since the preliminary emission is
variable, it is possible to realize preliminary-emission light
measurement capable of preventing a person to be photographed from
being dazzled. In addition, since the direct light of the flash
unit 18 is measured and the flash unit 18 is controlled so that the
amount of emission of the main emission can be made equal to a
correct integral value, it is possible to obtain stable and correct
exposure irrespective of the status or position of a subject or the
kind of photographic film.
[0509] If the shutter release button continues to be pressed with
the FE lock mode selected, the camera system can execute continuous
shooting at a constant amount of emission of the flash unit 18
(i.e., at the same amount of exposure).
[0510] In addition, after the FE lock mode is selected, if a
photographer performs an operation for altering photographic
conditions before an exposure operation, the FE lock mode is
changed to the batch emission mode and preliminary-emission light
measurement is again performed. Accordingly, it is possible to
obtain correct exposure suited to the changed photographic
conditions.
[0511] Incidentally, the present invention can be applied to a
camera system using an image recording medium other than
photographic film, and can also be applied to a camera system using
an image recording medium to which photographic information can be
written by a method other than magnetic recording.
* * * * *